Frequently Asked Questions: Feeding a CKD Cat

Compiled by Andrew Hall, updated April 14, 2024.

Disclaimer: Use the information in this document at your own risk. Although I make every effort to present accurate information in this document, I am not a veterinarian or nutritionist, and some of it is opinion rather than documented fact. I am not responsible for any errors or misuse of this information in the treatment of your cat. Always consult your veterinarian about what and how to feed your cat.

The questions and answers in this document have been compiled after years of answering the same questions, some many times, on the Feline Chronic Kidney Disease Facebook support group and seeing how people feed their cats and how the cats respond. I try to take a pragmatic approach to feeding cats and am skeptical of unproven claims and magic cures. I’m sure some will disagree with some of what I’ve written – sorry about that. Realize that it has been written after years of consideration, after reading about how hundreds of CKD cats – including my own, who died in 2021 – are fed and how they do on various foods.

There is a lot of repetition in the answers, on purpose, so that you may not need to read every answer to understand something. Personally, I learn better by repetition anyway.

Please email me at ahallfckd@bizave.com with comments and suggestions.

Introduction (read first!!)

What are the basics about feeding a CKD cat?

• Keeping your cat eating is the #1 goal, even if the food is not ideal. Many CKD cats have appetite issues and are too thin, so it is important to keep them eating something. If your cat eats a renal diet and does well on it, that’s fine, but if not…look for other choices. It is not better for your cat to lose weight and waste away because she is offered only food that is “good for the kidneys” that she may hate.
• Ideally, CKD cats should eat a low phosphorus diet, as low as reasonably possible in almost every case, even if the phosphorus blood test is low-normal. Try to find a few low phosphorus foods your cat loves. Renal diets are very low in phosphorus, but many cats hate them or won’t eat enough of them to maintain weight. Mature cats (the ones who usually get CKD) need very little phosphorus in their diets, and most cat foods have much more phosphorus than they need. Reducing dietary phosphorus intake helps keep the level of phosphorus in the blood in a low range, which can slow the progression of CKD and avoid some secondary health problems.
• CKD cats should eat a reduced protein diet (which is not the same as a “low” protein diet necessarily), though how low is too low is still a matter of some debate. Restricting protein is tricky because cats need protein! If they don’t get enough, they will lose weight and muscle mass. But more protein means more Urea (waste product from digesting the protein – often measured as BUN) building up in the body, since the kidneys can no longer remove waste products well anymore. This tends to worsen in the later stages.
• Don’t rely on the food label to figure out how much protein or phosphorus is in a food. You need to get more precise, useful information instead from the manufacturer (or from a food list that obtained it from the manufacturer). Most likely, you can’t look at a food label and say “this food is low in protein” or “this one is high in protein.” “Guaranteed analysis” percentages on a label are nearly useless at face value. Use “typical analysis” data instead, on a food list or on the manufacturer’s website (or contact them to ask for it). And don’t use “as fed” percentages (what is on a food label, sometimes what a manufacturer provides you) to compare foods. Use dry matter basis or a calorie basis instead, not “as fed.” If you don’t understand what any of this means yet…find the answers below in the list of questions.
• It’s important to feed enough calories on a daily basis! Don’t go by “ounces of food” or “cans of food” – every food has a different calorie content. If your cat is too thin, pay attention to the calories. Mature cats typically need about 20 calories per pound per day to maintain weight. Some senior cats may need even more than that. Add up the calories your cat eats if you worry she is losing weight (the calories are given on the food label in kcals); if she’s not eating enough calories, she’s going to lose weight, even if she seems to like the food you feed.
• If your cat is thin and you worry about her weight, get a baby scale to weigh her at home, to see if she gets enough calories from the current food. The “hold her while standing on the bathroom scale then subtract my weight” method may not be accurate enough to detect small changes in a cat’s weight.
• If your cat just won’t eat any food well, even “junk” foods, your cat may be nauseated, dehydrated, or have some other medical issue that must be addressed before she will want to eat. If you’ve tried a bunch of foods, even “junk” foods like Fancy Feast and she still won’t eat well, get your vet’s help. Don’t go too long searching for the perfect cat food she may finally eat. Treatments for nausea can make huge difference in a cat’s appetite. SubQ fluids can make a dehydrated cat feel a lot better and want to eat more. Both nausea and dehydration are common in CKD cats. Vets can prescribe appetite stimulants too, but they may not help if the cat is otherwise nauseated or dehydrated.
• CKD cats who have a ravenous appetite, yet who are still losing weight, may have some other untreated health issue like hyperthyroidism, diabetes, or IBD. This is especially true if the cat is eating far more than the typical 20 calories/lb/day most cats need to maintain weight.

The majority of CKD cats have appetite issues and tend to lose weight, so much of the guidance on this page is geared for those cats. If your cat is not underweight, not picky about food, and eating well, you will have a much easier time and many more food choices.

My cat is newly diagnosed and I am overwhelmed trying to understand – what should I feed?

CKD can be confusing and overwhelming. If you are getting confused about what to feed and find yourself going around in circles about cat foods…time out! The most important thing is to keep your cat eating, even if not the most ideal food at the moment. Many CKD cats live for months or years after diagnosis. Diet change for CKD is important, but feeding “not great” food for another few days or even a few weeks until you find a better food your cat will actually eat may not matter that much in the end. Feeding a CKD cat is a marathon, not a sprint. Pace yourself, give yourself time to learn and let things sink in.

Is your cat eating well – just not something good for CKD? OK, that’s fine. Aspire to feed a low phosphorus, moderately low protein diet, preferably not dry food. Start where you are and try to get to that. If your cat is eating wet food and eating something high in phosphorus like Fancy Feast, try a few new low phosphorus foods. See what your cat likes. Don’t try a dozen new foods the first week. (Transition slowly to a new diet! Cats can experience digestive upset if transitioned to a new diet too quickly.) Try two or three to start. If those don’t work out, keep feeding the old food and try a few more.

If your cat is eating dry food well and you want to transition him to wet food, don’t expect that to happen overnight if ever, unless he happens to love wet food. Many cats eating dry food are dry food addicts, and you may not be able to break the habit immediately. Many find that simply opening a few cans of wet food asking, “Do you like this one?” just doesn’t work. You may need a strategy and a lot of patience. Don’t starve your cat to force her to switch to wet tomorrow.

But if your cat isn’t eating anything well at the moment, even “junk” food like Fancy Feast, that’s something different. Many CKD cats suffer from nausea, may be dehydrated, have low blood potassium or high phosphorus, be constipated. All can cause poor appetite. Don’t expect simply switching diets to improve appetite or necessarily fix these issues.

There are lots of questions and answers on this page to help explain things when you have the energy to read some of them. Don’t try to understand everything in a day.

Renal Diets

What’s supposedly so great about a renal diet?

The two main attributes of a renal diet are reduced protein and very low phosphorus; less protein means fewer waste products like urea, and less phosphorus makes it easier for the kidneys to keep blood phosphorus under control. Reducing both can help your CKD cat. But there are other aspects to the renal foods that are supposed to help CKD cats. Some people dislike the high level of plant ingredients in renal diets, since they believe a cat’s natural diet is meat, not plants; but most vets still recommend renal diets.

Details

Your vet has the best of intentions in wanting your cat to eat a renal diet. Some cats do well on these renal foods. But many cats hate them or won’t eat enough of them; any supposed benefits are moot if the cat starves herself or wastes away because she won’t eat enough of it. There is nothing wrong with your cat if she loves Fancy Feast or other non-renal foods but hates renal food; it’s not the cat – it’s the food.

The low protein and low phosphorus content are the key aspects of a renal diet. (Why is restriction of protein and phosphorus helpful to CKD cats? See the other questions below.)

Even if you don’t feed a renal diet, it helps to understand the intended benefits of a renal diet even if you wind up not feeding one (or if your cat decides not to eat one), to help you understand what you’re looking for in a cat food for CKD.

First of all, renal diets are not “medicine” even though they are “prescribed” (in North America, anyway). They are simply diets formulated to meet the unique needs of CKD cats. (And they probably aren’t appropriate for cats without CKD – maybe the prescription keeps people from feeding them to cats without CKD.)

How are renal foods different from regular cat foods? They are made with less meat than a regular cat food, since the meat adds protein and phosphorus. In place of some of the meat is plant ingredients (in Europe, renal diets tend to be higher in fat with fewer plant ingredients than North American renal diets…but still low in protein) The plant ingredients like corn, rice, wheat, potato, have little protein in them but add carbs that replace the calories from some of the meat.

Some people think diets like these that are high in plant ingredients (carbs) are awful for an obligate carnivore cat. Cats can eat carbs for sure, but some cats handle them better than others. Some cats e.g. diabetic cats may do poorly on a high carb diet, and sometimes cats have bad reactions to the unusual ingredients.

There are other aspects to renal foods besides the reduced protein and phosphorus:

• “High quality protein.” The renal food makers claim that their foods use “high quality protein.” What they mean by this is: the protein is well digested, and fewer waste products are released. But this is a bit misleading. Meat itself is a “high quality” protein for cats. it’s the plant protein that is not necessarily “high quality.” Generally, a low carb “regular” cat food will be mostly meat protein and fat (unless you see a plant protein additive like “pea protein” or “potato protein.”)
• Added omega fatty acid supplements.
• Added calcium: all balanced cat foods have calcium in them (ideally, at least as much calcium as phosphorus), but renal foods tend to have a little more calcium than an average cat food (more calcium binds out some of the phosphorus).
• Added vitamins like B vitamins.
• Less acidity than a regular diet. Since many CKD cats tend toward acidosis, feeding a less acidic food can help CKD cats.
• More potassium than regular foods, since some CKD cats (not all!) have low blood potassium. Some renal foods are higher in potassium than others. (as of 2023, Purina NF renal foods are higher in potassium than Hills or Royal Canin. Some CKD cats have high potassium – so feeding Purina renal might not be ideal for them.)
• Additional vitamins, amino acids, and additives e.g. probiotics and omega fatty acid supplements that some believe can aid CKD cats. (You can add these yourself to your cat’s food if you don’t feed a renal diet.)
• Renal food makers pay closer attention to the nutritional content of their foods e.g. amount of phosphorus and protein than the makers of “regular” food. And they have done research to see how their foods affect CKD cats. (Makers of “regular” cat foods don’t do research to see how well CKD cats happen to do on them.) Most makers of “regular” cat foods usually aren’t designing the food to be good for CKD cats. If a “regular” cat food’s formula changes and goes up in phosphorus, that’s your problem – they usually don’t care as long as the food meets the AAFCO or FEDIAF nutrient profile. A maker of renal foods wouldn’t let that happen and will pay careful attention to things like phosphorus content.

Keep in mind you can add some of these supplements to any cat food e.g. vitamins, omega fatty acid supplements, and probiotics.

While all of the true renal diets are low in phosphorus (be wary of “renal diets” from off-the-wall companies that may not really be “renal foods” and may not be low in phosphorus! E.g. the brand with a “10” in the name makes foods that are not that low in phosphorus.), the protein content varies between renal diets. Some companies make “early” formulas that may be higher in protein than “regular” renal diets, though the added protein may be a vegetable protein like potato protein. Whether these high carb foods are better for CKD cats than a “regular” cat food that’s low in phosphorus is up to you and your vet to work out.

What kind of improvements in my cat’s well-being and blood work should I expect after switching to a renal diet?

You may not notice any improvements in your cat’s well-being from a renal diet. Some cats don’t even like them. The goal of diet change is not necessarily to affect any immediate improvement in your cat’s life – it’s more about trying to slow down the progression of CKD.

You may notice some improvements in your cat’s blood work after switching to lower protein diet than what you had been feeding before, e.g. a lower Blood Urea Nitrogen (BUN) or urea blood test, since more protein in the diet means more urea waste in the blood for the cat’s kidneys to remove. A very high urea/BUN (far above the normal limit in the blood work) is probably not good long-term for your cat, since it indicates urea building up in the blood…but a urea/BUN just slightly above normal (typically an early stage cat) may be OK. Lowering a just slightly elevated urea/BUN may not really have that much benefit.

You will most likely notice a lower blood phosphorus test too after switching to a lower phosphorus diet like a renal diet…unless what you were feeding before wasn’t that high. Some CKD cats already have a fairly low blood phosphorus at diagnosis anyway (early stages usually). The kidneys regulate the phosphorus in the blood and remove the excess in the urine (if they can). So if your cat’s blood phosphorus was low to start, a renal diet may not lower it much if at all.

If blood phosphorus was high at diagnosis, switching to a low phosphorus diet like a renal diet could lower it a lot, and that could make your cat feel better.

I wouldn’t expect much lower creatinine if at all from switching to a renal diet. Cats who lose muscle mass may have a reduced creatinine just from that – a lower creatinine due to muscle loss is nothing to celebrate.

Whether the SDMA test changes due to diet change may also be nothing to celebrate (or worry about), since the test can jump around, who knows why.

The most important thing is that your cat actually like the renal diet, if you choose to feed it. Some cats do well on renal diets. A cat who is losing weight on a renal diet after not losing weight on the old food is probably not liking the new food very well.

Should I feed my cat a renal diet, as long as my cat really loves the renal food and eats it well?

You don’t have to feed a renal diet to your CKD cat – some people don’t. It’s up to you…and your cat! But please read the other questions to understand what is important to feed CKD cats…and see the previous answer explaining what renal foods are and why vets believe they are beneficial.

Details

You may have read some disparaging comments about renal diets – e.g. the fact that cats might lose weight and muscle mass (see question below), the fact that the ingredients are not the best for cats in general, etc. Keep in mind that when someone says their cat lost weight on a renal diet, it may well be that the cat hated the food and barely ate it. It’s different if your cat loves it and gets enough calories from it vs. barely touching the food, right? Every cat is different.

It is very true that the renal diets are full of plant ingredients that are unnatural for cats especially in higher proportions – cats are obligate carnivores who eat birds and mice. Personally, I cringe when I look at the ingredients lists of these foods. I chose not to feed renal food to my CKD cat – she was sensitive to certain ingredients in cat food anyway, plus she was losing weight when she was diagnosed, and I just wanted her to keep/gain weight (and she did, for a long time). But I also hear plenty of stories of cats who have done well on the renal diets. How can I argue with those? Clearly some cats do well on them but many do not. Repeat: every cat is different.

I don’t think it’s a mistake to try the renal foods, as long as your cat really eats them well and gets enough daily calories from the food. (If your cat is losing weight, pay attention to the amount of daily calories you feed!) I believe (and many vets are starting to believe) that the biggest benefit from feeding a renal diet (vs. just feeding a low phosphorus food) would come in the late stages when the cat’s Urea/BUN is usually pretty high, not in the early stages.

But if your cat doesn’t like a renal diet, there’s no point in wringing your hands about it – the problem is with the food, not with a meat-eating cat who turns her nose up at a food full of corn gluten meal. Just find a low phosphorus food she will eat and do well on, as low in phosphorus as you can get away with. There are a lot of low phosphorus “non-renal” foods out there to choose from.

Will my cat lose weight and muscle mass eating a renal diet?

There have been many anecdotes about cats who have been fed a renal diet losing weight and muscle. People usually blame this on the low protein content of the renal foods. Is this true – and if so, why would my vet recommend renal food??

Before we can address the question about loss of muscle mass, we must remember that a cat has to like her food and eat enough of it to keep her weight – and that goes for every food you feed, not just renal food. She must eat enough daily calories, or she will lose weight and muscle mass – no matter what food she is eating. (You can calculate how many calories your cat eats a day – the calorie content is listed on the food label, in kcals. Every food and brand has a different calorie content.)

So let’s narrow the question: if my cat likes the renal diet and eats enough daily calories from it (typically 20 calories per pound per day to maintain weight), will she lose weight and muscle mass anyway?

Answer: I doubt it – but it’s possible. A few more things to keep in mind:

• Every cat is different. Some cats need more protein and calories than others.
• Every renal food is a little different – some renal foods are higher in protein than others.

Presumably, if someone’s cat is losing weight, they’ll offer the cat as much food as the cat will eat.

But, many cats hate the renal diets. Some cats do well on the renal diets, but many cats barely eat them. Some cats won’t eat any brand, at all. The North American renal diets are low in protein and high in carbs, the opposite of a cat’s natural diet. (Some European versions are low in protein, very high in fat, not quite as high in carbs). Offering more food that the cat hates isn’t going to help a cat gain weight, obviously – you have to feed them something they will eat.

Some cats eat more than enough calories a day to maintain/gain weight yet still lose weight. This could be caused by another medical issue like hyperthyroidism, diabetes, or IBD.

Otherwise, if a cat hates the renal diets, feed something else the cat will eat – but don’t automatically revert to feeding whatever your cat wants. Try to feed something low in phosphorus, anyway, if you can. Maybe you can find a”non-renal/non-prescription” low phosphorus food your cat loves. (If not – of course feed something “bad that the cat loves” if you have to to get her to eat – but it should be a last resort.)

You might be tempted to feed a high protein diet (high vs. “moderate” or “moderately low”) to get your cat who has lost muscle mass to re-gain it, but this may not be as helpful as you might guess. See the questions addressing these issues below. Again, remember: your cat needs not just protein but enough calories every day (fat, too, not just protein!) to maintain/gain weight.

Will my cat live longer on a renal diet?

Your CKD cat will probably live longer if you change the diet to keep the blood phosphorus low (instead of feeding a high phosphorus food like Fancy Feast pate) and if you are able to feed a reduced (not necessarily “low”) protein diet, to reduce the waste products from digesting protein like Urea from building up in the body. But you can achieve much of the same benefit without feeding a renal diet, by feeding cat foods that are almost as low in protein, almost as low (or lower) in phosphorus than a renal diet. If your cat hates the renal food as many do, she is probably not going to enjoy life if she loses weight and muscle if that’s all she is given to eat…and she may even live a shorter life.

But if someone says “your cat will live longer on a renal diet,” ask, “compared to feeding what?” Compared to feeding Fancy Feast pate that’s super high in phosphorus…and doing nothing to reduce blood phosphorus? Yes, on average, I’d guess that in that case, a CKD cat would live longer on a renal diet…if the cat likes the renal food well enough to eat it well. But every cat is different. Occasionally you hear of a CKD cat who has been eating Fancy Feast for years and blood phosphorus is still normal. And you also hear of plenty of cats eating renal diets who unfortunately don’t live long. That doesn’t mean Fancy Feast is good or renal diets are bad – these are really the exceptions. CKD progresses differently in every cat. Be wary of comparing your CKD cat to someone else’s and trying to feed what they fed if their cat was some sort of miracle CKD cat who thrived on Fancy Feast. (And don’t avoid renal foods just because someone else’s cat did poorly on them.)

But, there are studies comparing cats fed a renal diet to a “maintenance diet” and the results showed about double average lifespan (20.8 months vs. 8.7 months in one study, 16 vs. 7 months in another). But again, what was the “maintenance diet?” There are sooo many variables. Did all of the cats fed the renal diet like it and eat it well? Were any other treatments done? (My cat never tried a renal diet and lived almost four years after diagnosis at stage 3…would she have lived eight years if I had fed her a renal diet? Doubt it. Every cat is different.) I don’t see how feeding a renal diet to a cat who hates it is going to help the cat live longer or have a better life. (Some cats do like the renal foods, but many hate them and barely eat enough to avoid starving.)

And…which renal diet? They are not all the same either. Compare the protein content of Royal Canin, Purina, and Hill’s…all different! I can feed a lower phosphorus non-renal diet (Weruva Wx is lower in phosphorus than most of the renal diets) or add supplements to try to treat high phosphorus or low potassium in a “regular” food…or do nothing.

There are too many variables to say “every cat will live twice as long on a renal diet.” The cat needs to like the food and eat it well – we are not just trying to keep them alive, we also want our cats to keep eating and not lose weight if possible, to enjoy life too. If you try a renal diet and your cat loves it and does well on it…that’s great! Feed it. If your cat hates every renal diet you’ve tried and barely eats but happily gobbles down low phosphorus Weruva or some other low phosphorus food, by all means, feed the latter.

If my cat’s blood tests all improved after switching to a renal diet, doesn’t that mean the diet is “working?”

You have to interpret the creatinine and Urea/BUN blood tests along with the cat’s diet and body condition not just assume “lower is always better” or “higher is always worse.”

Details:

Maybe better blood tests indicate health improvement from the renal foods, maybe not…but you can’t look at just the blood tests. How is your cat doing? If you say switched your CKD cat’s diet from high phosphorus Fancy Feast to a renal diet and he gained some needed weight and seems to be doing better…and his blood tests improved, that’s quite different from saying you switched to renal food but he lost weight and doesn’t seem any better on it…just because the blood tests may have improved doesn’t necessarily the renal food is “helping” in the latter case.

Renal diets are low in protein and very low in phosphorus. If your CKD cat was eating a high phosphorus, moderately-high protein diet like Fancy Feast at diagnosis, then switching to a low protein, low phosphorus diet should certainly lower the blood phosphorus and BUN (Urea) tests, since Urea is a waste product from the breakdown of protein during digestion. Less protein means less Urea building up in the blood that the kidneys can’t remove as well anymore.

But remember that the main reason we run blood tests for creatinine and BUN – waste products the kidneys are just trying to get rid of from the body – is not because these waste products are so toxic but to see how much the kidneys can remove. Creatinine and BUN are kind of like yardsticks to tell us how much the kidneys can remove. All else being equal, if creatinine and BUN go down, that generally means the kidneys are able to remove more so are probably working better in general; if creatinine and BUN go up, we assume the kidneys are able to remove less than before and not working as well.

But if you change the diet to reduce the protein and the body now makes less Urea waste as a result…there is just less Urea waste for the kidneys to remove. So a lower Urea/BUN test in that case doesn’t mean the kidneys have improved at all. (Though less Urea building up in the body is probably good for the cat.)

By comparison…if say you don’t change the diet at all (so the protein intake is the same) and you start a treatment like SubQ fluids and BUN (and creatinine) declines significantly…that probably does mean the kidneys are removing more BUN now so presumably working better. See the difference, vs. the body just making less BUN from a lower protein diet?

Creatinine is less affected by diet than BUN. A change in creatinine should be interpreted in part along with any significant change in the cat’s weight and muscle mass. Creatinine comes largely from the normal breakdown of muscle, so if a cat loses weight and significant muscle, the body will produce less creatinine waste. (And conversely, if a cat gains significant weight and muscle, expect a higher creatinine test, but that may not be bad!) Many CKD cats do lose weight and muscle mass, sometimes due to being fed a diet they hate and don’t eat enough of, so we shouldn’t say “Hey, the blood tests improved!”and celebrate in that case.

You have to interpret the creatinine and Urea/BUN blood tests along with the cat’s diet and body condition.

Be careful about attributing an improvement in your cat to one specific thing. If your cat was treated for a UTI, started some other supplements or treatments like SubQ fluids, and started a renal diet…it may that not all of these had the same benefit for your cat.

Phosphorus

Why is phosphorus bad for a cat with kidney disease?

When cats get CKD, their kidneys can’t remove excess phosphorus from the blood well anymore and phosphorus starts building up, potentially leading to faster progression of CKD and other health problems. Feeding a low phosphorus diet makes it easier for the kidneys to manage the phosphorus levels.

Details

Phosphorus is an essential mineral for life. Cats need some in their diets, but mature cats don’t need much. Phosphorus digested from the food is absorbed into the blood, and excess phosphorus is removed by the kidneys. All cat food has meat in it, and all meat contains at least some phosphorus. Most “regular” cat foods have far more phosphorus in them than mature cats need. (Kittens need phosphorus to grow, so kittens should not eat a low phosphorus diet.)

Healthy kidneys are good at regulating the level of phosphorus in the blood and removing excess phosphorus absorbed from the food, in the urine. But when cats get CKD, their kidneys struggle to remove the excess phosphorus, and it eventually starts to build up in the blood. This tends to worsen over time as the kidneys decline. (Some CKD cats do have low-normal blood phosphorus though, at least in the early stages; blood phosphorus tends to tick up over time in CKD cats.)

So feeding a low phosphorus diet helps the struggling kidneys by making their job easier and not having excess phosphorus building up in the blood, where it can cause health issues.

For more details about what happens with phosphorus in CKD cats, please find the excellent article “Calcium Phosphorus Balance in Dogs and Cats” by Wendy Brooks, DVM, DABVP (from 2007, probably on VIN, google for it).

What is considered “low phosphorus” in cat food?

Renal foods contain about 100 mg/100kcal (100 mg of phosphorus for every 100 calories) of phosphorus or about 0.5% Dry Matter Basis – that is considered very low. By comparison, Fancy Feast pates are around 400 mg/100kcal or 2.0% Dry Matter Basis – that is considered very high. Close to 100 mg/100kcal or 0.5% DMB is low.

Details:

There are various phosphorus guidelines you can follow, but many are ridiculously strict. E.g. one guideline suggests limiting phosphorus to 0.3% to 0.6% Dry Matter Basis…which means only renal diets, with very few other exceptions. AAFCO specifies a minimum phosphorus of 0.5% Dry Matter Basis in adult cat foods (not CKD cats), but most are much higher than that. Many cats are picky and don’t like any of the renal diets nor some of the non-prescription foods that are low in phosphorus. It’s pointless to insist on a tight phosphorus restriction if your cat won’t the foods that are that lowest very well.

Don’t use “as fed” percentages to assess the phosphorus! They are diluted by the moisture. If a wet food is 0.25% phosphorus “as fed,” and moisture is 78%, that may seem low, but that is not low in phosphorus! On a dry matter basis, that would be 1.14% DMB, which is more than 2X higher than a typical renal diet. See this article to read more about percentages and dry matter basis.

But, you can compare “regular” foods to renal diets, which are about as low in phosphorus as you can get. Let’s say a typical renal diet is 0.5% Dry Matter Basis or 100 mg/100kcal (mg of phosphorus per 100 calories) – I prefer mg/100kcal since I find it corresponds better to how much phosphorus cats actually ingest from their food. But…if a food is 200 mg/100kcal, then it is 2X higher than a typical renal diet. If you use Dry Matter Basis, then a food with 1.0% DMB is about 2X higher than a renal diet.

What if your cat won’t eat the foods that the very lowest in phosphorus? Then find something your cat will eat, even if it’s not that low. Low phosphorus is preferred, but your cat has to eat. Just do the best you can! Maybe the best you can do is a food that’s 2.5X higher than a renal diet. That’s better than one that’s 3X or 4X higher (like Fancy Feast pate, which is about 300 – 400 mg/100kcal on average).

How do I know how low or high a cat food is in phosphorus?

You usually can’t tell just from the food label whether a food is low in phosphorus. Sometimes there is a phosphorus percentage on the label, but even that can be misleading if you don’t know what it means. It’s best to get the phosphorus information directly from the manufacturer, as a “typical analysis,” and you want to use a dry matter basis or calorie basis (mg/100kcal) to assess the phosphorus, not the “as fed” percentages on the food label. Sometimes the manufacturer puts a good nutrient profile on their website; sometimes you have to contact them to ask for phosphorus info. Sometimes you will find it on a food list.

>>>Calculate Dry Matter Basis or mg/100kcal Using This Calculator

Details

Most regular cat foods like Fancy Feast aren’t low in phosphorus. (Renal prescription diets are very low.) If your cat was just diagnosed with CKD and you are wondering if what you already feed is low enough for a CKD cat, try first to find it the info on the manufacturer’s website or on a food list that is up to date. (Foods can be reformulated and phosphorus can change; don’t rely on an old food list for this information.) If you can’t find it otherwise, you can contact the manufacturer and ask. (What to ask for? See below.) If you live in the US, Chewy often lists phosphorus info for foods they sell in the “Questions” section, though be wary of inaccurate information there. (I’ve seen wildly wrong phosphorus answers on Chewy more than once.) If in doubt, verify with the manufacturer.

You probably won’t have any clue by looking at the food label how much phosphorus is in it. You can’t tell from the ingredients list. Some cat foods contain phosphate additives that add more phosphorus to the food, but the meat will have phosphorus in it too. (And Ash is not the same as phosphorus! Ash tells you nothing about the phosphorus content.) All cat food has some phosphorus in it (all meat has phosphorus in it, and all cat food has meat in it). Sometimes a phosphorus percentage is included on the label as a percentage…but even then, that might not mean what you think it means. (Keep reading.) Most likely you’re going to need to get more precise phosphorus info e.g. from the manufacturer or from a list of low phosphorus foods.

If there is a phosphorus percentage on the label, it is probably a minimum percentage (foods sold in the US market), and most people use typical/average values to assess phosphorus, not minimums. It’s really best to get a typical analysis value for the phosphorus, and you want to convert any “as fed” percentages on a label to dry matter basis or use a calorie basis. If the guaranteed analysis is all you have, see below for a way to estimate an average phosphorus for it.

The percentages on food labels are always “as fed” – but you have to use dry matter basis or a calorie basis (mg/100kcal or g/1000kcal) to assess phosphorus (or calcium, or any other mineral). “As fed” percentages on food labels and that you sometimes see in a nutrient profile are diluted by the water in the food and useless for comparing foods! If a wet food is 0.2% “as fed” phosphorus with 78% moisture, that’s a lot higher in phosphorus than a dry food with 0.5% “as fed” phosphorus and 10% moisture. If you use dry matter basis or mg/100kcal, this difference will be obvious!

To read more about the difference between “guaranteed analysis” and “typical analysis” and the difference between “as fed,” dry matter basis, etc. please read this separate article.

The phosphorus content is different for EVERY cat food even of the same brand! Some brands do make foods that are mostly low in phosphorus…but you still need to find out the phosphorus content of each food – don’t assume every food from one brand is low!! E.g. Weruva makes a lot of low phosphorus foods, but some of their foods are quite high! Pay attention to the specific food names.

What do I ask for when contacting a pet food company for phosphorus info?

Most manufacturers provide a phosphorus percentage for their food if you ask them for it. But it’s important to understand that a percentage can be either “as fed” (diluted by the water in the food) or “dry matter basis” (the moisture factored out). If you are new to this, ask them for the phosphorus on a dry matter basis. Yes, dry matter basis applies even to wet food.

If they give you only the “as fed” percentage, it may seem really low, and you can’t compare foods using “as fed” percentages (because they all have a different amount of water in them). You can compare the foods on a dry matter basis – even compare the phosphorus level of a wet food and dry food. You can convert the “as fed” percentage (if that’s all they give you) to % DMB easily using a % DMB calculator. All you need is the moisture percentage.

Please read this page to learn more about dry matter basis vs. as fed percentages.

Sometimes they will give you the phosphorus on a calorie basis – mg of phosphorus per 100 calories (mg/100kcal) or grams per 1000 calories (g/1000kcal). This is fine too but harder to calculate (personally, I find the calorie basis more useful and precise than % DMB, but either will work).

>>>Calculate Dry Matter Basis or mg/100kcal Using This Calculator

How can I estimate phosphorus if all I have is the guaranteed analysis (minimum)?

It’s really best to try to get a typical analysis (average values) since this is a more accurate view of how much phosphorus (or protein, or anything) is in the food. If a food is say 0.7% (minimum) phosphorus according to the guaranteed analysis on the food label, it could be considerably higher than that on average and after you convert it to a dry matter basis! See if the manufacturer has the typical analysis instead! (Check their website, might be in a “nutrient profile.”)

But what if you just don’t have anything but the guaranteed analysis?

Here’s a way you can guess at the average/typical percentage from the minimum (not for protein – only for minerals like phosphorus). This may not apply to foods not sold in the US markets…but, several US food manufacturers have told me that their minerals like phosphorus will be no more than 50% higher than the minimum. In other words, if the phosphorus is given at 1.0% (minimum), the highest it would be would be 50% higher – 1.5% (1.0 x 0.5 = 1.5%). From that we can guess that 25% higher would be an average/typical value. (A guess – again, really best to ask the manufacturer for a typical value if you can.)

So let’s say a bag of dry food has a phosphorus listed as 0.9% (minimum). 25% higher would be 0.9 x 1.25 = 1.125% (typical/average).

However…that’s “as fed.” You still need to know what it is on a dry matter basis or a calorie basis (mg/100kcal).

If the bag says 10% moisture, then the dry matter basis of 1.125% phosphorus would be 1.25% DMB.

For the calorie basis, mg/100kcal (mg of phosphorus per 100 calories), you need the Metabolizable Energy (ME) – this is almost always on the food label (in kcal/kg – calories per kg). Let’s say this food shows as 3,724 kcal/kg. Then the phosphorus (again, a guess) would be 302 mg/100cal. (Spoiler alert: this food is quite high in phosphorus. Since renal diets are around 0.5% DMB or 100 mg/100kcal, this food is about 2.5X to 3X higher in phosphorus than a renal diet!)

Actually, this is a real food. And the manufacturer also provides a typical analysis in addition to the guaranteed analysis on the bag. So we can see how far off our guess was: instead of our guess of 1.125% “as fed,” they say it is only 1.07% “as fed” with 7.5% moisture…so the dry matter basis would be 1.16% DMB. That’s a tad bit lower than our guess but not far off. And the mg/100kcal comes out to be 288 mg/100kcal. (Still too high.)

Can’t I just add a phosphorus binder to my cat’s food and feed whatever my cat wants?

A “phosphorus binder” is something you can mix into the cat’s food to prevent some of the phosphorus in it from being absorbed during digestion. Some common binders include aluminum hydroxide powder and calcium-based binders like Epakitin (or Ipakitine outside of North America).

Please note: phosphorus binders are usually not recommended unless your cat’s blood phosphorus test is elevated, no matter what you feed. The purpose of the binders is to help the kidneys keep the level of phosphorus in the blood low. But some early stage CKD cats may have low-normal phosphorus even if they eat high phosphorus foods like Fancy Feast.

While many people use binders for CKD cats, they have drawbacks. First, even though some binders are supposedly odorless/tasteless, some cats do seem to detect them if added to their food and may refuse to eat it. Second, they can cause side effects like constipation. And depending on what the binder is made of, it can raise the levels of certain things in the blood. (Some binders like Epakitin are calcium-based; don’t use a calcium-based binder if your cat’s blood calcium is say elevated already, since elevated calcium is not uncommon in CKD cats.)

Please don’t start using a binder without chatting with your vet.

The binders don’t bind out all of the phosphorus, either. If you are feeding Fancy Feast pate (which may be about 2% phosphorus on a dry matter basis), a good binder might bind out up to half of it so might make it equivalent to about 1% DMB…which is better than 2% of course, but not as good as just feed a low phosphorus food that’s even lower than 1% DMB without a binder. If your cat will eat one that’s low, of course.

Plus, some CKD cats especially in the early stages still have low blood phosphorus and may not need to have it lowered anyway.

It’s simply a much better idea to feed a low phosphorus diet in the first place, if you can get your cat to eat one. But if you can’t get your cat to eat any low phosphorus food, he’s got to eat something well, even if it’s Fancy Feast pate. In that case, make sure his blood phosphorus test is run each time you get blood work done, and if the blood phosphorus rises too high, then get your vet’s advice on adding a binder.

My cat’s last blood phosphorus test was normal – do I still need to feed a low phosphorus diet?

Some people assume that because their cat’s blood phosphorus falls below the maximum level of the blood report’s reference range, that therefore the phosphorus is perfectly fine and nothing to worry about. But the reference range in the lab report has nothing to do with CKD. It’s just that lab’s reference range for cats.

Instead, your vet should follow treatment guidelines on how to assess phosphorus levels for a CKD cat. E.g. the IRIS treatment recommendations for CKD cats (as of 2023) recommend keeping blood phosphorus between 2.7 and 4.6 mg/dL (or 0.9 to 1.5 mmol/L international). This is usually a far narrower range than the lab report. (e.g. a lab report may show a phosphorus of 6.0 or 7.0 mg/dL as “high normal” even though that’s too high for a CKD cat, according to IRIS.) This IRIS recommendation is based on research suggesting CKD cats have a better survival time if their phosphorus is kept in that range. (Not every vet follows the IRIS guidelines.)

What if your cat’s blood phosphorus is very low, even within the IRIS range? Then I’d still aim for a low phosphorus diet…as always, provided your cat will eat it. Keeping your cat eating is always the #1 priority. If my cat’s blood phosphorus is higher than the IRIS range, I’m going to try much harder to find a low phosphorus food she likes than if her phosphorus very low.

Even if you can’t get your cat to eat a low phosphorus diet, maybe you can at least find foods that aren’t that high. Except in rare cases where a CKD cat’s blood phosphorus is really too low, for a mature cat there is no benefit to all of the extra phosphorus in most regular cat foods. Maybe your cat hates some of the lowest phosphorus Weruva foods but will eat something lower than Fancy Feast.

CKD treatment guidelines regarding phosphorus are evolving, and not all vets are keeping up with the changes. IDEXX has a new blood test out (as of 2023) called FGF-23 (“phosphorus overload”), and the recommendation is to restrict phosphorus intake e.g. use a phosphorus binder if FGF-23 is elevated even if the blood phosphorus itself is very low. Whether this new test will prove to be useful remains to be seen – but it does suggest being even more strict about phosphorus intake from the food than past recommendations.

How much phosphorus in the food is OK or too much for a CKD cat?

Beyond aiming for “as low as possible,” it’s hard to give an acceptable phosphorus percentage that’s good for every cat (“below this percentage is OK, above this percentage is too high”), because every CKD cat is different, and as the CKD progresses, phosphorus restriction becomes even more important. So phosphorus is kind of a moving target.

Sometimes you will see strict phosphorus guidelines for CKD cats such as “below 0.5% dry mater basis or below 100 mg/100kcal.” Basically that means a renal diet with few exceptions – and in many cases, it’s impossible to get your cat to eat something this low anyway. (Whether or not you should feed a renal diet is another question.) So if you can’t meet such a strict requirement, you still might ask, “How low can I get away with?”

The biggest worry with phosphorus is too much building up in the blood. If your cat’s last blood phosphorus test was low normal (below the IRIS guideline of up to 4.6 mg/dL or 1.5 mmol/L), then you have more freedom to feed a not-as-low phosphorus diet, at least for now. (Please read the question above regarding what a “normal” blood phosphorus test really means.)

It would still be best to feed a food as low as possible to any CKD cat if you can. But, there are usually trade-offs when feeding a CKD cat. The cat may not like certain foods of course. Or the cat may have other conditions that restrict what you can feed other than for CKD. And some people simply dislike the low phosphorus, low protein renal diets in general. If your cat’s blood phosphorus is below the range mentioned above, you have a little freedom to feed something higher in phosphorus if you have to or want to, for now. Just make sure your cat’s blood phosphorus is tested every time your cat has updated blood work!

That doesn’t mean you should ignore the phosphorus level in the food if the last blood test was low! I’d still avoid high phosphorus foods if your can – but maybe you can feed something not-so-low at least.

But if your cat will eat a low phosphorus food and you don’t have a lot of other worries, why not feed a low phosphorus diet? If you can, I would, even if your cat’s blood phosphorus is low.

See the related questions above about phosphorus in food.

Is “natural” phosphorus OK (e.g. in raw meat) but only the phosphorus in canned/ dry food is bad?

Some people claim that “natural” phosphorus is not harmful for a CKD cat – that only the phosphorus in commercial/canned food or kibble must be bad. I don’t quite know where this idea comes from – I can only assume people are thinking of the phosphate additives included in some foods.

All phosphorus that is consumed in any type of food, whether it is in raw meat or canned food, has to be removed (except the small amount a mature cat might actually need – only kittens really need much, as they grow), mostly removed by the kidneys. But the phosphorus in different elements of the food is absorbed differently. Some of it is not absorbed into the blood during digestion and is passed out through the gut. Most of the phosphorus in most cat food is in the meat or the bone (the “meat” ingredient in most cat foods usually includes bone, unless it is explicitly called “boneless meat.”). Many cat foods contain phosphate additives as well e.g. tricalcium phosphate (a phosphate similar to what’s in bone, added to balance the calcium and phosphorus in the food).

Cooking the meat (to make canned food or kibble) doesn’t turn the phosphorus into “bad phosphorus” that is somehow worse for the kidneys; feeding it raw doesn’t mean it is “good phosphorus” that is easier for the kidneys to remove.

It’s true that the phosphorus in the additives is absorbed more fully – and quickly – than the phosphorus in meat (or plant ingredients). Whatever phosphorus is in the meat or plant ingredients is not fully absorbed into the body (as much as the phosphate additives are), but presumably much of it is. The same phosphorus in food that is “bad” for CKD cats who get more than they need is “good” for kittens who need it to grow. So the kittens must be able to absorb the phosphorus from the meat – if they can, so can a CKD cat, no matter what the source. And if the phosphorus is absorbed into the blood, no matter where it came from, excess has to be removed (mostly by the kidneys).

There is some controversy over how bad phosphate additives in food might be for cats in general. Some research suggests the additives may be bad for the kidneys, but subsequent research has found no harm. In any case, what matters most is how much of the additive is in a cat food, not the mere presence of any amount. (As an analogy, cats must get vitamin D from their food, but too much would be toxic for them.) If a food has a low overall phosphorus content and you see tricalcium phosphate as ingredient #12, there can’t be much of the phosphate in there. But if the food is high in phosphorus and you see tricalcium phosphate as ingredient #4 (ingredients are listed in order of weight, so higher generally means more of the ingredient), you would be more worried, since there is probably a good amount of tricalcium phosphate in that food.

Some commercial raw diets include phosphate additives too FYI – check the ingredients if you really want to avoid them.

But don’t assume “natural phosphorus in raw meat is OK” but only phosphorus in commercial food is bad. There is zero evidence that this is true.

Protein

Why is protein “bad” for a CKD cat?

When protein is digested, waste products like Urea are released and build up in the blood in CKD cats, whose kidneys can no longer remove them as well. The more protein in the diet, the more waste products created. The more of these waste products that build up, the bigger the impact on the cat’s overall health – and this gets worse in the later stages of CKD (higher Urea/BUN blood test). This is why your vet probably recommended switching your cat to a low protein renal diet.

Details:

When my cat was first diagnosed with CKD, I knew zero about CKD and diet. My vet explained that reducing the dietary protein meant that the kidneys “don’t have to work as hard.” What she meant, apparently, was that less protein results in fewer waste products from digesting protein building up in the blood, since the declining kidneys can’t remove them well anymore.

My vet was trying, I guess, to spare me a complicated explanation I might fail to understand at a time when I was overwhelmed trying to come to terms with my kitty’s CKD diagnosis. But her analogy was a bit misleading.

It’s not that every bit of protein your cat eats damages the kidneys a little more… or that the kidneys “burn out” the more protein the cat eats. (The kidneys don’t “filter protein” anyway.) Rather, it’s that the more the kidneys decline, the less waste they can remove from the blood, including the waste products like Urea from digesting protein. The real issue is high levels of Urea and other waste products building up in the blood that cause problems for the whole body, not just the kidneys. The body is a finely tuned machine that works as intended when the kidneys can filter most of the waste out, but when the kidneys struggle and waste products build up, things gradually start to go wrong.

In the early stages of CKD, the kidneys generally can still remove most of the waste they could before. In terms of protein, the Urea or Blood Urea Nitrogen (BUN) blood test indicates how much Urea is left in the blood. There is always Urea in the blood even of a healthy cat. There’s just more building up when the kidneys struggle. There will likely be much more excess Urea in the late stages than in the early stages. A higher BUN/Urea blood test indicates higher levels of Urea.

The more protein in the diet, the more Urea waste created, the more the kidneys have to remove (or…the more excess they can’t remove anymore). This is why many vets recommend a low protein renal diet. Whether a low protein diet is helpful or necessary in the early stages when Urea/BUN is probably not that high is questionable. The cat’s body is probably able to compensate when there is just a little extra Urea building up vs. a lot of extra Urea in late stages, when BUN/Urea is probably going to be quite high.

Cats need protein, so it’s a tricky balance between too much vs. not enough protein. (See separate questions below.)

But a high protein diet is probably not a great idea for any CKD cat, if you can avoid it, at any stage, since a high protein diet would create a lot of extra waste like Urea. And a high protein diet may not have much benefit for a CKD cat anyway. (This is addressed in some other questions. Please read to learn what a “high protein” diet really means!)

The other possible complication from CKD involving protein is proteinuria (protein leaking into the urine). Many CKD cats seem not to develop proteinuria, though, even in the late stages. Your vet in addition to a regular urinalysis can run a Urine Protein to Creatinine (UPC) ratio test or a microalbumin test to see how much protein is leaking if any – there should be almost none. (The ratio should be very low.) These urine tests aren’t always run in a CKD cat. The “protein” test in a regular urinalysis is not always accurate enough to assess proteinuria.

Note that there are some people who believe protein restriction for CKD is pointless and that dietary protein has zero consequence in a CKD cat, that high levels of Urea mean nothing, that low protein diets may actually be bad for CKD cats (for example, if it causes them to lose muscle mass). Protein restriction for CKD is controversial. Whether you choose to restrict protein is something you’ll have to decide for yourself – but please read the question below “How much protein is too much?”

Still, there is some research suggesting that high levels of Urea are bad for humans with CKD. (There is always so much more research done for human CKD of course.) While people aren’t the same as cats, we can assume a lot of the same issues apply. Google for the excellent article “Urea is truly toxic: the empire strikes back” by Wei Ling Lau, UC Irvine, on Atlas of Science for details.

So feeding a reduced protein diet can help reduce the level of Urea building up in the blood. (And may help cats with proteinuria). Just remember: if you choose to restrict protein, you don’t have to feed a renal diet. There are low protein foods, high protein foods, and many in between. But please make sure you understand what “low” and “high” protein means as explained in one of answers below. (don’t use the food label percentages to compare foods!) And don’t forget you need to restrict phosphorus, too!

How much protein is enough?

Cats need a significant amount of protein in their daily diets, more than dogs or people need in theirs. And since cats are obligate carnivores (must eat meat), it’s harder to restrict their protein. If cats don’t get enough protein, they will lose weight and muscle mass and develop other health issues. But is there really a percentage or amount that works for every cat?

Details:

AAFCO stipulates a minimum of 26% protein on a dry matter basis for adult cats but only 18% for dogs. Renal diets for dogs can therefore have less protein in them than for cats.

Many people believe that renal diets are too low in protein for CKD cats, though that is controversial. Renal diets are anywhere from 28%-35% protein on a dry matter basis (on average around 25% of calories from protein), so based on that, they are all above the AAFCO minimum, probably higher than some people realize. So assuming a cat likes a low protein renal food and eats enough of it to eat enough calories (typically about 20 calories per pound per day to maintain weight), in theory renal diets should have enough protein for the cat to sustain weight. Again, if the cat eats it well.

But there are studies suggesting that some senior cats may need even more dietary protein as they age and may not be able to digest and use protein as well as when younger. Some people even believe cats need a minimum of 40% of calories from protein to maintain muscle mass (this seems very high to me; my CKD cat’s diet was much lower than this for years and she kept her muscle mass quite well for a senior cat). So opinions vary on this.

Clearly, every cat is different – some cats probably may need more protein than others. If your cat is newly diagnosed with CKD, though, it’s a bit unnerving not to have a clear answer on how much protein is OK or how much is too much. No one wants their cat to lose muscle mass if possible, but they don’t want to further damage their cat’s kidneys, either.

Who do you believe, with all of these conflicting opinions? It seems so confusing, doesn’t it? You’ll drive yourself nuts after a while trying to figure it out, the more you read. But remember that the main thing is that your cat has to eat, preferably something low in phosphorus, and many cats are picky and may not even eat the lowest protein options (mostly renal foods) anyway. If your cat won’t eat a low protein food, there isn’t much point worrying about it.

It’s easy to become obsessed over protein for your CKD cat. But don’t forget the calories. Cats also need enough calories in their daily diet to avoid losing weight, matter how much protein they eat. That means your cat has to like the food enough to eat it well (whether it’s a renal diet or not), no matter how low or high in protein it is. Mature cats typically need 20 calories per pound per day to maintain weight (sometimes more – again, every cat is a little different).

You’ll have to decide what to do about protein – follow your vet’s advice? (probably “feed a renal diet”) or choose something else. I would probably err on the side of a little too much protein vs. a little less, especially if I could find a food my cat really liked and ate well. I would try to avoid a high protein diet though. (What “high protein” means is the answer to another question.)

I would remind you that because cats need the same amount of daily calories no matter how much or little protein you feed, less protein means more fat and/or carbs. All calories in food come from protein, fat, and carbs, so you can’t restrict one without increasing one or the other two. This is why low protein renal diets are either very high carbs or (primarily in Europe) very high in fat. Some people worry more about carbs than fat – depends who you talk to.

How much protein is too much?

The other side of the protein coin besides “how much is enough?” is, “how much is too much?” We discussed the possible drawbacks of a high protein diet for CKD cats above. You’ll have to decide what you believe there (since some people don’t believe in protein restriction for CKD at all). I definitely believe protein matters especially in the later stages, to keep the Urea (BUN) from getting too high and would want to limit protein at least somewhat, as long as I can keep my cat eating well and keeping her weight and muscle mass. (If she is keeping her muscle mass, why would I find the need to feed a diet higher in protein?) Make up your own mind.

I know many people want a specific percentage, a target to aim for, “Below this percentage is OK, above this percentage is too much.” I’m sorry, I don’t have one I believe works for every CKD cat. (Some strict guidelines for CKD cats recommend keeping protein between 28%-35% Dry Matter Basis, which basically means a renal diet only, with a few exceptions.) I think it’s probably a different answer for every cat, and that answer may change as the cat ages. I’m really more worried about making sure my cat eats well and eats enough daily calories to maintain or gain weight, not just enough protein.

I definitely want to feed enough protein for my CKD cat to maintain her weight and muscle mass – but I don’t see any benefit from feeding more than she needs. The cat’s body doesn’t have an unlimited ability to build muscle mass, so doubling the protein intake doesn’t double the amount of muscle mass. When protein is digested, some of the liberated amino acids are turned into glucose to be burned for energy or stored as fat. If my cat is eating enough protein for basic needs, the excess is just burned for energy or used for fat, I’d rather just feed a diet with less protein, more fat, since fat is much more calorie-dense than protein…and digesting fat does not produce more waste products like Urea! If I am trying to get my cat to regain lost weight, I want to feed enough protein – and calories! – but if she will eat enough food, a food higher in fat, a little lower in protein, should help her gain it more quickly. (Worried about fat and pancreatitis? please read the question below addressing that.)

I see increased protein as a sliding scale with more Urea/BUN. A diet a little higher in protein means a diet a little higher in Urea. If I fear that a renal diet is too low in protein, I’m also not going to feed a super high protein diet (like Tiki Cat) either – I don’t want the extra Urea, and I’d rather have my cat eat more fat, less protein. There are many foods in between a low protein renal diet and a super high protein diet. I would err on the side of a little too much protein vs. not quite enough. (And of course, I want to feed a diet low in phosphorus, too!)

Please read the answer below about what a “high protein” food is and how to compare foods! (Not via the food label!)

Most vets don’t calibrate the cat’s dietary protein intake with blood tests like Urea/BUN…but you can use that as a guide. In the early stages, Urea/BUN tends not to be very high yet (not far above the lab’s reference range, if at all). The cat’s body is better able to compensate for a little more Urea than normal vs. a lot more than normal as is common in the late stages. I’ll also want to make sure my cat doesn’t have proteinuria – but if my cat does not have very high Urea/BUN and no proteinuria, I’m going to worry a lot less about restricting protein.

(Note: the blood test “Total Protein” has little to do with whether the CKD cat is eating too much protein or not! There are always proteins in the blood. A high Total Protein test could indicate dehydration, but a high Total Protein blood test does not mean “must feed a diet lower in protein!!!”)

There is probably no “percentage” of dietary protein that suits every CKD cat.. At very least, avoid a high protein diet if you can, even if you don’t feed one that’s “low.: Again, do the best you can with feeding to keep your cat eating, even if the protein is higher than you or your vet would like.

What is considered a low protein diet? What is considered high?

Don’t go by the food label protein percentages which are misleading. Use ME Profile (percentage of calories from protein, fat, carbs) or Dry Matter Basis to assess protein, and that’s never on a food label. Find that info on the manufacturer’s website or on a food list (or contact the manufacturer). Renal diets are roughly 25% of calories from protein. A “regular” cat food that is only 30% of calories from protein is not much higher than a renal diet. A food that is 50% of calories is obviously 2X higher.

Details:

Please read the answer about food labels and why you can’t tell from the percentages on a food label whether the food is low or high in protein. You need to use a dry matter basis or, even better, Metabolizable Energy (ME) Profile – percentage of calories from protein, not “as fed” percentages or guaranteed analysis.

I prefer to use ME Profile to check protein, since it corresponds better to how much protein a cat actually ingests. (A cat who eats 200 calories a day ingests more protein from a food that is 40% of calories from protein than one that is only 30%.) Dry Matter Basis is still much more useful than an “as fed” percentage.

As a baseline, let’s use the renal diets since they are about as low in protein as you could safely feed any cat (some believe they are too low…but that’s another discussion). And renal diets are roughly 25% of calories from protein (or roughly 28%-35% dry matter basis). So I compare every food to that.

You will probably see several Weruva foods on any low phosphorus food lists for North America. Let’s look at the protein content of a few common Weruva foods: Weruva BFF OMG Cloud 9 is about 29% of calories from protein, so not really much higher than a renal diet. BFF PLAY Checkmate is about 32%, just a little higher. Weruva Wx are around 40% of calories from protein, so significantly higher than the renal diets. Weruva Steak Frites is about 45%. Weruva Paw Lickin’ Chicken is probably their highest protein “low phosphorus food” at about 65% of calories from protein – so that’s quite a bit higher than renal food, about 2.5X higher.

At the extreme, Tiki Cat After Dark (not the pates) are very high in protein – about 70% of calories from protein. Remember, 70% of calories from protein means 30% of calories from fat, at most, which is quite low. Fat is not bad for cats – it is easy to digest and high in calories. So a low fat diet is usually not good for a CKD cat.

Most dry foods are not very high in protein. Some exceptions would be low carb foods like Young Again, Dr. Elsey’s, and Wysong Epogen 90 (North America) which are very high in protein, something like 45% to 55% of calories from protein.

Most raw diets tend to be fairly high in protein too. E.g. Lotus raw foods vary from about 40% to 50% of calories from protein.

Lean meat like chicken breast is very high in protein, low in fat. (Boneless chicken doesn’t have much phosphorus – the bone adds a lot of phosphorus.) Chicken thigh is lower in protein, higher in fat, so in general better for a CKD cat if the cat would eat it.

Why can’t I rely on the food label to see if the food is low or high in protein?

Two problems with the percentages on a food label: they are “as fed” (diluted by the water in the food) and they are minimums/maximums, not averages. It is best to get a “typical analysis” (sometimes called “nutrient profile”) – averages, not minimums/maximums – from the manufacturer. And to compare percentages, you need to convert them to a dry matter basis or a calorie basis, since the water diluting the “as fed” percentages makes them difficult to compare directly.

Details

The percentages on a food label (at least in North America) are “Guaranteed Analysis” and can be quite misleading. Guaranteed analysis is an FDA labeling requirement, which can tell you how much of something is in the can or bag but not how much of it your cat will consume! Big difference there. Every cat food has a different calorie content, and your cat might need to eat more cans per week of one can than the other, if it is a lower calorie food.

Here’s an example: suppose I have two equal size 100 gram cans of cat food but different recipes or brands. Both cans say “9.0% protein (minimum) on the label” Which one is “lower” in protein?

Each can has the same amount of protein: 9% (at least). If the cans are 100 grams then each can will have 9 grams of protein it. (100 x 0.09 = 9 grams .)

But…your cat may not eat the same number of cans of each food every day! If one can is a lot lower in calories than the other, then you’ll need to feed more cans of the lower calorie food. Your cat should eat about the same number of calories a day. Just because each can has the same amount of protein doesn’t mean each can has the same number of calories (cat food also has fat and maybe carbs in it).

Let’s say, in an extreme case, that one of these two foods has double the calories of the other…even though both are 9% protein. If one can has double the calories of the other can, then your cat has to eat twice as many cans a day of the lower calorie food. If your cat needs to eat only one can (9 grams of protein) of the higher calorie can, she will need to eat two cans of the other (and get 9 + 9 = 18 grams of protein).

Here’s another example: Have you ever wondered why dry foods seem to be a lot higher in protein than wet foods? They aren’t. The reason it may seem so is because there is almost no moisture in a dry food to dilute the protein percentage. Wet food is about 75% water, which dilutes the percentages of protein, fat, etc. a lot.

This is why “as fed” percentages that you see on a food label are useless for comparing foods. They are diluted by the water in the food and don’t tell you anything about calorie content (how much your cat must eat a day). Instead, you need to use a calorie basis or a dry matter basis to compare foods. Then, the difference between foods will be obvious, and you can compare wet and dry foods on the same basis.

You won’t find a calorie basis or dry matter basis on a food label, unfortunately. It is easy to calculate dry matter basis or a calorie basis if you have just the “as fed” percentages. There are dedicated calculators that do the math for you; all you have to do is plug in the percentages. (See below.) Sometimes you can find them compiled on a cat food list.

The other issue with guaranteed analysis – minimums/maximums – is that usually averages or typical values are used to compare foods, not minimums. It’s best to get a typical analysis (aka nutrient profile) from the manufacturer. Sometimes it is on their website. You will never find a typical analysis on a food label, either.

>>> To read more about guaranteed analysis and the difference between “as fed” and dry matter basis, read this article.

Can’t I use a supplement like Azodyl or Porus One and feed any amount of protein I want?

There is no such thing as a “protein binder” as there is with phosphorus, something to add to food to “mask out” protein from being absorbed…but there are a few supplements that claim to be something close. Azodyl is a probiotic/prebiotic combination supplement (modeled on a human supplement) that is supposed to absorb some of the waste products from digesting protein. Some people swear by this product and insist it has greatly helped their cats. Others have not noticed much benefit. And there’s really not a lot of proof that it is overall effective. (or that another probiotic might be just as effective). Azodyl is expensive, too, and not supposed to be given with regular cat food – it’s a big capsule that some cats might hate getting.

Porus One is not a probiotic but is similar in approach – a charcoal-based supplement that is supposed to absorb some of the waste products that result from digesting protein. Again, as with Azodyl, some people swear it has helped their cats. Others haven’t seen big benefits with it. And there isn’t much scientific backing to prove it is effective or extends the cat’s lifespan, either.

So who knows if these really work to “reduce the protein” (waste products)? I have looked at a lot of blood work reports from cats with CKD, and I have yet to see one where the BUN noticeably declined after the cat started either supplement.

It’s possible these supplements help some cats but not others. Presumably, waste products from protein digestion are already partly eliminated in the gut even without any supplements. Could be a probiotic like Azodyl enhances this ability. Maybe Porus One does also? Who knows.

But let’s assume they do help. Does that mean you can ignore dietary protein and feed as much as you want and not worry about it? No! These supplements don’t even promise to get rid of all of the waste products. Even if they reduce the BUN, they obviously don’t reduce it to the levels of a healthy cat. Feeding a reduced protein diet, if you can get your cat to eat one, is guaranteed to reduce the BUN. If these supplements help reduce it more, great. There’s probably no harm in trying them (if you don’t use Azodyl, starting some other – cheaper probiotic is probably not a bad idea).

Will a high protein diet help my cat regain lost muscle?

As mentioned in the previous answers, you can’t look at just protein: you have to make sure your cat eats enough calories per day! (At least 20 calories per pound per day to maintain!) If your cat isn’t eating enough daily calories, she will lose weight and muscle mass, no matter how high in protein the diet is. If you feed too few calories, most of protein in the food you feed must be burned for energy.

Could feeding a diet higher in protein than the low protein renal diets help, though? Maybe, as long as you can find a food your cat really loves and will eat enough of to meet the daily calorie need. But feeding something higher in protein than a renal diet doesn’t mean you have to feed a high protein diet! Renal diets are around 25% of calories from protein. At the other extreme is something very high like Tiki Cat After Dark at about 70%. I’d aim for closer to 25%, not closer to 70%. You can read about the drawbacks of a high protein diet in another answer.

Keep in mind that your cat doesn’t have an unlimited ability to build new muscle. Just doubling the amount of protein in the diet doesn’t mean the cat builds twice as much muscle. Muscle can only be built so quickly. Feeding a diet super high in protein may have little or no benefit at all and may even make it harder for your cat to re-gain weight and muscle, because high protein foods are so much less calorie-dense than lower protein foods with more fat.

For example, let’s say your cat got sick of eating low protein renal food and has lost some weight and muscle. You could feed your cat two different foods that he loves: Weruva BFF PLAY Chicken Checkmate (about 32% of calories from protein) or Tiki Cat After Dark Chicken in Broth (68% of calories from protein), so more than twice as much protein. A 5.5oz can of Checkmate has 197 calories in it. A 5.5oz can of After Dark (only 128 calories). You will have to feed 1.5x as many cans of Tiki Cat as of Checkmate a day. Will he even eat 1.5x more of the TIki Cat every day?

You presumably want your thin cat to eat as much food as possible a day. If he likes both of these but his appetite is iffy, maybe he will eat more Checkmate a day – and get even more calories. Getting him to eat more Tiki Cat a day will be harder since you’ve got to feed 1.5x more of it. And of course, the higher protein produces more Urea (BUN) (which you may or may not accept as something that causes problems for CKD cats when BUN is very high – see the previous answers to questions about protein.)

Is a higher protein diet higher in phosphorus too?

Not necessarily!

Strictly speaking…yes, a piece of lean (high protein) boneless meat has more phosphorus in it than a less lean / more fatty piece of boneless meat.

But while the meat is a primary source of phosphorus, in cat food, bone and phosphate additives (e.g. tricalcium phosphate) can also increase the phosphorus content significantly. While you’ll see the phosphate additives listed by name in the ingredients, usually you won’t see “bone” listed even though it’s often part of the “meat” ingredient like “chicken.” Unless it says “boneless chicken,” assume the “chicken” has bone mixed in.

And bone is actually healthy for cats without CKD – it’s part of a cat’s natural diet. (Cats eating their prey eat the bones, too). The bones have phosphorus and calcium that a cat needs. But…the added bone adds extra phosphorus that isn’t good for a CKD cat.

So…yes, it’s possible to have a high protein cat food made with boneless meat that is fairly low in phosphorus while a lower protein food could be higher in phosphorus. If you are looking at a cat food, don’t assume it must be low or high in phosphorus based on the protein content.

My vet says all Weruva foods are too high in protein for CKD cats – is that true?

Weruva makes over a hundred different wet foods (sold mostly in North America). Each one has a different protein (and phosphorus) content. Some like BFF OMG Chicken Cloud 9 (29% of calories from protein) and BFF PLAY Chicken Checkmate (31% of calories) are not much higher than the renal diets (which are about 24%-25% of calories from protein). Some Weruva foods are much higher. Weruva Wx is roughly 40% of calories. Some like Weruva Classic Paw Lickin’ Chicken are very high at 65% of calories, more than twice as high as the renal diets.

So it’s wrong to generalize that they are all too high in protein.

The issues with a high protein diet are explained in other answers. While your vet is right to worry about protein, it’s not an “either-or” proposition. If your cat hates the renal diets and will barely eat one, it’s not “bad” for them to feed a Weruva food they happen to love that’s not much higher in protein than the renal diets…but feeding one super high like Paw Lickin’ Chicken is probably not a great idea if your cat will eat something lower in protein. As always, the main goal is keeping your cat eating with something as low in phosphorus as you can get away with…even if it turns out to be a Weruva food not that low in protein. Do the best you can.

Types of Food

Why do people frown upon feeding dry food to a CKD cat?

Mostly due to the lack of water in dry food. Because cats with CKD need to drink a lot of extra water to make their kidneys work and pee a lot, CKD cats are prone to dehydration, since they lose so much water in their urine.

Dry food obviously has very little water in it. Cats eating wet food get a lot of water just from the food, since wet food is about 75% water. (A 5.5oz can of cat food has roughly 110ml to 120ml of water in it.) Healthy cats eating a wet food diet get most of their water from their food and may not need to drink much more, if any, additional water. But cats eating dry food must drink water to stay hydrated, even if they don’t have CKD. When they get CKD, they need to drink yet more water.

Obviously no one wants your cat to starve if he refuses to eat wet food – feed him dry food if you have to. Some cats are dry food addicts. You may be able to get him to start liking wet food…or maybe not. But if he eats wet food well, see if you can find a low phosphorus wet food he will eat well, for at least some of his diet if not all.

Some vets recommend renal dry food, presumably because they want the cat to eat a renal food, and most cats seem to find dry food irresistible but often reject the renal wet food.

Is it possible your CKD cat can eat an all-dry diet and still drink enough (probably quite a lot) to stay hydrated? Sure, it’s possible. Every cat is different. Maybe your cat can eat dry and drink enough. But dehydration is more likely; you are relying on your cat to drink plenty of water every day. If you feed wet, if your cat eats wet, the cat is guaranteed to get a certain amount of water just by eating the food.

Cats are not naturally heavy water drinkers, since in nature they get most of their water from their prey. For a cat to have to drink so much extra water day after day must be fatiguing for them. Who knows if your cat will be able to keep that up for a long time? Maybe.

That’s why dry food is discouraged, especially for CKD cats. Getting them to eat at least some wet food requires them to drink less water separately and makes dehydration less likely.

Some people try really hard to get their dry food addicts to switch to wet food – and sometimes they succeed (hint: it usually takes more than just opening a few cans of wet food and hoping your cat likes one; it may take a strategy and a lot of time and patience! Stop free-feeding dry food, to start). But if your dry food addict cat starts losing weight because he hates the wet food he is now fed and doesn’t eat enough, that’s obviously not good either!

It may or may not be worth trying to switch your stubborn cat to wet food by the time CKD is diagnosed – up to you. Just feed dry food if you must to keep your cat eating. And do your best to encourage more water drinking – add an extra water bowl or a fountain. Experiment with different types of water bowls. (Purina makes a supplement called Hydra Care that may be of most benefit to cats eating a dry diet.) But if he likes wet food, feed him that if you can or at least some wet food.

Why do people think dry food / kibble is so bad for cats (unrelated to CKD)?

There are a number of reasons some people don’t like dry food for cats. The biggest reason is probably the lack of water discussed above. A cat’s natural diet – a mouse or a bird – provides most of the moisture a cat needs. Cats evolved from desert creatures who did not always have access to plentiful water; drinking a lot of water routinely is not natural for them. A lack of water in the food means they have to drink extra water to compensate, and some cats just may not drink enough. Their urine may become too concentrated, and issues like crystals can develop.

The other big issue people worry about with dry food is the high content of plant ingredients like corn, peas, or potato used to make most cat foods, and this make them high in carbs. Cats being obligate carnivores, their natural diet is meat. They can eat plants (unlike certain types of wild cats who are completely unable to digest plants), but domestic cats are not well adapted to eat plants like humans are. Their digestive tract is shorter than a human’s – and while meat digests pretty quickly (less time in the digest tract), plants take longer to break down, which is where a longer tract helps. A cat’s saliva does not contain amylase (enzyme) that helps to break down starches.

But, not all plants are digested in the same way. Pet food makers try use plant ingredients that are as digestible as possible by cats. But no matter what they do, the plant ingredients still aren’t meat. Plants are high in carbs and low in protein (FYI, “corn gluten meal” is purified corn protein), and the protein they do contain does not have the same amino acid profile that meat protein has (cats can’t make some amino acids like taurine – they must get it from their food).

Plus, some cats have reactions to some plant ingredients like grains. While there is no proof that a high carb plant diet causes diabetes in cats, it seems clear that a high carb diet is likely to trigger it in cats predisposed to be diabetic. (Join a Facebook support group for diabetic cats, and you will see cats diagnosed with diabetes who had been eating high carb dry food, over and over and over again. Is it really a coincidence?) When you feed a high amount of unnatural ingredients to a meat eater, we shouldn’t be surprised that some cats can’t handle them well.

Still, not every cat develops health issues from eating dry food. But these are the biggest concerns. (To read more about why some people dislike dry food, look up the Catinfo website from Dr. Lisa Pierson, DVM. She is not a fan of dry foods, to say the least!)

Of course, people have reasons to feed their cats dry food. It is cheaper than wet food (some people live on a very tight budget), and and it is super convenient just to set down a bowl of dry food and just let your cat eat. (Some cats don’t live in an indoor home situation.)

But maybe the biggest reason people feed dry food is that their cats won’t eat wet food! It can be hard to persuade a dry food addict to switch to a wet diet – maybe not really worth the stress for a senior cat with CKD already. Depends on the cat. (It is probably not as simple as just “open a few cans of wet food and hope the cat likes one! It takes a strategy and some patience.) The cat has to eat something, and if she won’t eat wet food, and if you’ve already tried to switch a dry food addict to wet food, there’s no point in losing sleep over it . Just feed dry if you have to to keep your cat eating and do your best to keep her hydrated.

But what does a high carb diet have to do with CKD? Probably not much, once a cat already has CKD. There are some people believe dry food causes CKD, but there is no research to support this. (Lots of cats eating an all-wet or even a raw diet develop CKD too.) The more plant ingredients in the food, the more of the protein is from plants, the less from meat, so that reduces the “quality” of the protein. Some believe that oxalate that comes from digesting plant ingredients can cause kidney disease, but this is not widely accepted.

Will my cat drink less water after switching from dry food to a wet diet?

Yes! Dry food has almost no water in it, obviously. Wet food is about 75% water. A 5.5 oz (156 gram) can of food has roughly 120 ml or about 4oz of food (depending on the moisture content of that particular food) So if your have stopped feeding dry and replaced that with one 5.5 oz can of water a day…that means your cat needs to drink 120 ml less water! Or, if your cat has CKD, he may wind up drinking less but maybe not 120 ml less, since CKD cats need to drink extra water anyway, no matter what kind of food they eat.

Healthy cats eating only wet food may drink little or no water at all.

What about raw feeding? Good or bad for CKD cats?

A cat’s natural diet is truly a bird or a mouse – raw – not a can of cooked cat food. Some people believe that feeding raw meat (a balanced raw diet, not just muscle meat alone) is best for all cats, including CKD cats. But many vets are appalled by the idea of raw feeding at all, maybe worried about certain bacteria or parasites in raw meat that would be killed by cooking it.

Let’s put aside the question of whether raw feeding is good for cats in general (over all of their lives) – you’ll have to decide that for yourself. The topic of raw feeding tends to elicit passionate opinions. If you already have a strong opinion, you probably will find something in this answer to disagree with. Sorry!

The questions here are: is raw feeding specifically good for CKD cats, because the food is raw? If you aren’t already feeding a raw diet, should you switch to one if your cat is diagnosed with CKD? Or, if your cat has already been on a raw diet prior to CKD diagnosis, should you continue on it?

As someone who is not a raw feeder myself (but not opposed to raw feeding in principle), I try to take an agnostic approach to the idea of raw feeding. I know more than one person who has fed their cats a raw diet for a long time without any negative consequences. I also know numerous cats with CKD who have been or were fed raw for a while and seemed to do well on it. But…I know of no evidence or research showing that feeding a raw diet (because it is raw) is better for a cat with CKD. (Just because someone “insists” it is true, doesn’t mean it is.)

So if you decide to switch your CKD cat to a raw diet, you won’t be able to do it strictly on the basis of science. On the other hand, if someone scares you with the idea that “raw is bad for CKD cats!” I know of no research indicating that is bad, either! I know more than one person who fed their CKD cat a raw diet for quite a long time, too. If your cat is immunocompromised or has a disease like FIV, you may wish to avoid raw food, though.

But there is one case where switching your CKD cat to raw might be a good idea, though, and that is: because your cat is not eating anything else well. Some picky CKD cats who turn their noses up at any canned food seem to thrive on raw food – they may find the smell and taste of raw meat irresistible. Indeed, switching to a balanced raw diet is most definitely something I would try if your cat stops eating anything else well. Remember, eating well is our #1 goal! We don’t want them to waste away – of course I’ll feed my cat who has ignored a dozen different kinds of canned food a balanced raw diet if he loves it. Why wouldn’t I?

Please remember though that you still need to worry about protein and especially phosphorus in a raw diet! Regarding the phosphorus, the most important thing is to make sure the food is made without bone! Bone is a primary source of phosphorus in cat food (even in canned food – even though it’s not broken out in the ingredients list, bone may be part of the meat ingredient.) A balanced diet for cats needs calcium, though, and boneless meat has very little calcium in it; most commonly eggshell (aka calcium carbonate) is used to add the calcium. (Calcium balances the phosphorus in the food and binds some of it during digestion.) Some raw food makers also use phosphate additives like tricalcium phosphate (similar to what’s in bone) or even sodium phosphate. I would definitely avoid raw foods made with bone or made with phosphate additives.

If your cat had already been eating raw food prior to diagnosis and was otherwise doing well on the diet? I’d probably keep feeding raw – but again, minus the bone and using eggshell for the calcium.

As far as the protein, try to use fatty cuts and leaner meat (if you make your own food). Fat is usually good for cats and very calorie-dense – digesting fat does not release the same waste products that digesting protein does.

There are not many commercial raw diets that are low in phosphorus. Some are not bad. Most are made with bone. Most freeze dried raw cat foods are high in phosphorus.

Please remember that your raw diet must be balanced!!! So you can’t just feed them raw chicken breast – there are ways to balance the raw food to make it complete and healthy, with all of the vitamins, minerals, and amino acids a cat needs to be healthy. And be wary of goofy raw food recipes you find on the internet – some of them are not healthy for cats!!

Can’t I just feed a “senior” cat food if my cat won’t eat a renal diet?

No, not necessarily! Remember, the main issue with food for CKD cats is the blood phosphorus. Some “senior” cat foods are actually quite high in phosphorus e.g. Purina’s. Some are low in phosphorus, yes. Just don’t rely on the “senior” branding and assume that therefore the food must be OK for CKD cats. Check the phosphorus in any food you want to feed, even a senior food.

The other issue with some “senior” cat foods is that they may be designed to be low in calories for inactive cats who might tend to gain weight. But a typical CKD cat tends to be too thin, not too heavy! Be wary of the calories if your cat is too thin and needs to gain weight. It’s actually OK to feed a low phosphorus senior diet to a CKD cat if it’s not high in calories, as long as your cat eats enough of it!

Don’t blindly feed a “senior” food to your CKD cat – always check out the phosphorus, protein, and calorie content.

Can I feed “kitten food” to help my kitty gain weight? Isn’t kitten food super high in calories?

Feeding a high calorie food can be helpful to a thin CKD cat, but kitten foods are not a great first choice! They tend to be high in phosphorus (since kittens need phosphorus to grow, it’s good for them!).

Lots of cat foods that aren’t “kitten foods” are high in calories!!! There are plenty of other high calorie foods that aren’t kitten foods.

You don’t have to guess at the calorie content of the food and think that “kitten foods must be higher in calories than anything else.” Look at the calorie content of each food – it’s right on the food label, in kcals. There’s also something else on the food label called Metabolizable Energy (ME) – this is the calorie content by weight (kcals/kg – calories per kg fed) instead of the absolute number of calories in the can or bag. In general, the higher the ME, the more calorie-dense the food is.

For example, Weruva, who makes a lot of low phosphorus foods, makes some kitten foods, too. Some of their kitten foods are quite high in calories…but some aren’t that high. E.g. their Chicken & Pumpkin Formula has 87 calories in a 3oz can…which is really not bad, but it’s not as high as some of their other foods. Weruva BFF PLAY Chicken Checkmate has 87 calories in a 2.8oz can…but is lower in phosphorus. Weruva BFF OMG Chicken Cloud 9 has 101 calories in a 2.8oz can. Assuming your cat would eat the BFF versions, why would you feed the kitten food?

If you are desperate to get your cat to eat because she’s eating nothing at the moment…of course I would feed any cat food, including a kitten food, if you have to, if your cat loves that over anything else. Just don’t start with kitten food because you think it must higher in calories than other foods – it may not be any higher. Don’t feed a high phosphorus kitten food when you might feed a low phosphorus food that’s high in calories instead. Try to find low phosphorus, high calorie (i.e. high fat) foods that your cat really likes.

Can I feed “urinary health” food to my CKD cat? Should I?

You probably shouldn’t feed “urinary health” food to a CKD cat, unless your vet has a specific reason to prescribe it. These foods tend to lower the urine pH, and in CKD cats, the urine pH is often too low already – you don’t want to worsen it!

A few of these “urinary health” foods are not that high in phosphorus, though, and if your cat likes one of them and the last urine pH was more high than low (above 6.5), then maybe you can get away with feeding one. Definitely confirm that with your vet, though.

Can I feed my cat baby food?

Meat-based baby food (without garlic, onion, or lemon juice) is perfectly fine to feed to cats as a treat or a topper or for short-term feeding. It is not a complete/balanced diet for cats, though, so you shouldn’t feed it for a long period as the only food. If your cat is really struggling to eat anything at the moment, though, feeding a meat-based baby food is a lot better than feeding nothing. It’s just far from ideal.

The phosphorus in these baby foods may not be very high, but there is also no added calcium to balance the phosphorus, so more of the phosphorus would be absorbed. (Calcium binds to phosphorus, so the more calcium in the food, the less your cat absorbs from eating it.)

It is possible to balance baby food to feed it to a cat as the primary food.

Can I feed renal dog food to cats?

No! Renal food for dogs is much lower in protein than renal food for cats, so much too low for cats. This is because dogs need much less protein in their diets than cat do.

General Questions

Is my cat nauseated, or is she just getting picky about her food? Or just tired of it?

Depends. Does she have a favorite food she used to love before CKD? If she still devours the old food – even if that food is too high in phosphorus for a CKD cat, then her appetite is probably just fine. If she won’t eat other foods she used to love anymore, presumably she is nauseated, dehydrated, or otherwise not feeling well, so whatever is causing her to not feel well must be addressed.

Many CKD cats become nauseated at some point, though. Vets can prescribe medications like Ondansetron (Zofran) or Cerenia or over-the-counter meds like Famotidine (Pepcid AC) and Omeprazole (Prilosec). Ask your vet before giving your cat any over-the-counter med!

Many CKD cats also become dehydrated and many will need regular SubQ fluid therapy at some point. Dehydration is another reason for poor appetite.

Cats can have other issues like high blood phosphorus, low potassium, or anemia that would show up in blood tests.

A cat who has suddenly stopped eating anything, for more than a day, could have pancreatitis, which is very dangerous and not something to fool around with. Cats can’t go weeks without eating – they need to eat enough on a regular basis to avoid getting Hepatic Lipidosis (fatty liver).

But if your cat eats her old favorite food just fine, maybe try to find something else she likes better that is a little lower in phosphorus, even if not the very lowest phosphorus food out there.

Is it OK to feed foods labeled “intended for intermittent or supplemental feeding only?”

Weruva Wx and Dave’s Restricted Phosphorus are OK. Applaws (wet) and Reveal are not.

Details:

Most cat foods sold are complete and balanced for cats. They have adequate vitamins and minerals and other nutrients cats need. Foods made for the US market must include a “statement of nutritional adequacy” on the label, per FDA requirement. Most pet food makers choose to meet an AAFCO nutrient profile, and you’ll usually see “AAFCO” on the food label.

But some foods can’t meet an AAFCO profile, and you may see wording like “supplemental feeding only” or “complementary food.” Foods wind up being labeled this way for different reasons. Some pet foods aka “natural” pet foods are just meat and don’t include important vitamins, minerals, and amino acids cats require in their daily diets. It’s OK to feed them as a snack or for a short time but not for a long time as the primary food. For example, almost every cat food contains added taurine, since cats must get it in their diets, and cooking meat (a good source of taurine when raw) can ruin some of the taurine. Cat foods should have adequate calcium in the food, and most cat foods do not and will include some sort of calcium supplement.

There are two foods sold in the US market (may be available in Canada and elsewhere also) often fed to cats with CKD: Weruva Wx Phos-Focused and Dave’s Restricted Phosphorus. These two foods are complete and balanced, except for the low phosphorus, but that’s exactly what we want for CKD cats! You can feed them every day to CKD cats with no other foods. They are potentially too low in phosphorus for cats without kidney issues – or at very least, too low to meet the AAFCO minimum requirement. (If sold in Europe, both would probably meet the FEDIAF minimum requirement for phosphorus, since FEDIAF’s requirement is lower than AAFCO’s for adult cats.)

But other foods you may find like Applaws (wet food) and Reveal are not balanced, and should not be fed as the primary, daily food. Check the ingredients!! There actually may not be much phosphorus in these foods, but since there is no added calcium, more of the phosphorus in them will be absorbed.

Other brands like Almo Nature make some foods that are “complete” and others that are “natural” (not balanced). Check the ingredients list!

It’s a shame that unbalanced cat foods like Applaws and Reveal wind up with the same “intermittent or supplemental feeding only” label that balanced foods like Weruva Wx contain, but it’s important to note the difference!

How much water does my cat get from a can of cat food?

Cat food is measured by weight, not volume. So you can tell how much water is in the can by the weight of the food in it e.g. 5.5oz (or 156 grams).

One ml of water weighs 1 gram.

Since a typical cat food is about 75% water, then 156 grams of wet food has about 117 grams of water in it. (156 x 0.75 = 117.) For simplicity, let’s say 120 grams of water in a typical 5.5oz/156 grams can of cat food.

So, the 120 grams of water equals 120 ml of water per 5.5oz can. But every cat food has a different amount of moisture, so this is just a baseline guess. Some 5.5oz cans may have 110 ml or even 100 ml if they have less moisture; some with a higher moisture content may have 130ml or more. Weruva makes a food called Grandma’s Chicken Soup which is 84.5% moisture, quite high. So a 5.5oz can of Grandma’s Chicken Soup would have 156 x 0.845 = 131.82ml of water in it.

What can I feed to my healthy cat now to avoid CKD later?

No one really knows what causes feline chronic kidney disease. People have a lot of theories, but few of them have much basis in science. Some people believe feeding a dry food diet causes CKD. While personally I don’t recommend feeding a dry food diet to your cat in general, I know of no proven connection between CKD and a dry diet. (But dry food might cause other health issues – e.g. cause a cat predisposed to diabetes to become diabetic or urinary crystals.)

I also know of no research proving that feeding a raw diet prevents CKD. Maybe it does, but there is no evidence. Plenty of cats who have been fed a raw diet since they were kittens still develop CKD. And plenty of cats who have eaten just low-quality kibble all of their lives wind up not getting CKD or not until they are very old, by which time most cats probably have some renal insufficiency. Perhaps it’s genetic, the luck of the draw, just as some smokers never get lung cancer while some non-smokers still do.

There is some known connection between dental disease and feline CKD, so I would get your cat’s teeth cleaned when she needs that done.

Beyond that, remember there are other health issues besides CKD. Feeding a wet (or raw) food or mostly wet food diet is probably healthier for most cats than feeding dry food.

How do I calculate how many calories my cat is eating, and what’s the right amount?

Cats need a certain amount of calories a day to maintain their weight, more to gain! The calorie content of every food is different – usually listed on the food label (in kcals).

Details:

Why bother to figure out how many calories your cat is eating? If your CKD cat is not thin and not losing weight, you may not need to worry about the number of calories you feed. But if your cat seems to be eating well yet still losing or not gaining weight? Then try to figure out your cat’s daily calorie intake. In my experience, many cat owners have no clue how many calories their cat eats every day.

Mature cats typically need to eat about 20 calories per pound (or about 45 calories per kg) per day just to maintain weight. E.g. an 8lb cat needs about 160 calories a day just to maintain weight, more to gain. If you wonder why your 8lb cat who used to be 10lbs is losing weight and you figure out she is eating only 140 calories/day…that’s not enough calories to gain, probably not enough to maintain 8lbs.

It doesn’t matter how many cans you feed if you don’t feed enough calories. Every food has a different calorie content, even of the same brand. The calorie content is listed on the label, in kcals. (Which are calories for our purposes.) For example, Weruva Classic Grandma’s Chicken Soup has only 106 calories per 5.5oz can. Weruva BFF OMG Chicken Cloud 9 has almost 2X the calories: 197 calories per 5.5oz can. So you’d need to feed twice as many cans of Grandma’s Chicken Soup as of Cloud 9 a day.

The 20 calories per pound per day suggestion is a rough guideline, certainly not set in stone. Some cats may need more. If you google for “cat calorie requirements,” you’ll find a whole variety of calorie calculators that will contradict each other and confuse you the more of them you read. Who is right, if they disagree?

Let’s put it this way: your cat’s body is “right.” If your cat is losing weight, she is probably not eating enough calories. If she is gaining, she is eating more than enough (unless you want her to gain). If she is maintaining her weight (weight may fluctuate a bit up and down by a few ounces), she’s eating the right amount, at least to sustain that weight.

Weighing your cat regularly at home makes it much easier to understand if the current calorie intake is sufficient. I recommend a baby scale. I have found that holding my cat while standing on the bathroom scale then subtracting my weight is not accurate enough to detect significant changes in a cat’s weight.

What if your cat is eating far more than 20 calories per pound per day and still losing weight? Some cats may have undiagnosed medical conditions like hyperthyroidism, diabetes, or IBD that can cause weight loss despite eating more than enough calories. But before you consider those things, start with figuring out how many calories your cat eats a day now. “My cat is losing weight” is not a basis to suspect hyperthyroidism if she’s just not eating enough calories.

Example: let’s say your cat is 8lbs and eats only wet food. Then she needs to eat about 160 calories/day to maintain weight, more if you want her to gain. That’s about one 5.5oz can of Weruva BFF PLAY Chicken Checkmate (169 calories). If your cat is too thin at 8lbs and you want her to gain, then one can of Checkmate is not enough. If she weighs 6lbs and is too thin then if she loves Checkmate and eats a full can a day, she ought to be gaining weight from eating 169 calories/day from a whole can. (If she doesn’t like Checkmate, that’s a different problem…try to find another food she likes better!)

Let’s say she only eats dry food and you want to see how many calories she eats every day? The calories in dry food are listed on the label too, but they are usually given “calories per cup” or “calories per kg” (kcals/kg). If you have a kitchen scale, you can weigh the food bowl every morning and check the weight of the bowl. (Get a notebook and start writing down the weight every morning.) If the bowls weighed 300 grams (including the bowl) yesterday and weighs 270 grams today, then your cat ate 30 grams of food. If the bag says the food’s Metabolic Energy (ME) is 4,000 kcal/kg (or 4 calories per gram), then 30 calories is 30 x 4 = 120 calories, not enough for an 8lb cat who needs about 160. If she eats 40 grams, that’s 40 x 4 = 160 calories. (That’s an example for one food – not every dry food has an ME of 4,000 kcal/kg, check the bag for the ME of a particular food!)

You should weigh the bowl this way a few days in a row and average the weight change. (And if you add dry food the bowl, record the amount you’ve added, using the kitchen scale.) If your cat eats 30 grams today, 40 grams tomorrow, 35 grams the next…the average is about 35 grams/day.

Maybe your cat eats wet AND dry? Just combine these approaches, add up the wet and dry separately. If she eats half a 5.5oz can of Checkmate that’s about 85 calories (half of 169 mentioned above) every day and eats 20 grams of dry food that’s 4,000 kcal/kg (20 x 4 = 80 calories), that’s about 165 calories/day, so that’s probably enough for an 8lb cat to maintain, more to gain.

Obviously, if your cat is thin and will eat more of the food if offered, feed more! Some cats need more than 20 calories per lb per day to maintain. If your cat doesn’t like the current food, find another food she likes…or if she is nauseated or dehydrated, treat that if she just won’t eat enough of anything.

And yes, if you are feeding more than one cat together, this can be much harder to work out! You still might be able to guess if you have two cats sharing the same dry bowl. In this case, track the daily calorie intake of both cats and weigh both of them. Let’s say you have one healthy cat and one CKD cat. If the healthy cat’s weight is stable and in total both cats are eating 400 calories/day, and the CKD cat is losing weight…then you need to increase the 400 calories that both eat. This is definitely not a perfect method.

And to repeat: If your cat is thin and is eating a lot more calories than 20 calories per pound per day and not gaining, he may have some other issue like hyperthyroidism, diabetes, or IBD – ask your vet!

What do I feed if my CKD cat is also diabetic?

CKD cats need to eat a low phosphorus diet. Diabetic cats should eat a low carb diet. Unfortunately, the low phosphorus renal diets are mostly high in carbs, and many typical off-the-shelf low carb pates like Fancy Feast and Friskies are very high in phosphorus. There are some foods low in both, but not many (in North America, most are made by Weruva…and some cats don’t like Weruva foods at all.)

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The carbs in the diet affect the blood sugar especially in diabetic cats. A high carb diet requires more insulin. Many diabetic cats are on a low carb diet to try to minimize spikes in blood sugar.

Renal prescription diets are very low in phosphorus, which is great for CKD cats, but they are also high in carbs (at least the North American renal foods), which is not great for diabetic cats.

If your cat is on insulin already with no expectation of diabetic remission, it’s possible you might be able to adjust the insulin dose and ride out the increases in blood sugar from the higher carb load from a renal diet. But you could also simply seek a non-renal diet that is low in carbs. Some low phosphorus diets are very high in fat so not very high in protein or carbs. if your vet is adamant about a low protein diet, you could compromise and find a moderately low protein food that’s high in fat and a lot lower in carbs than a renal diet…and of course, low in phosphorus. Consult an updated food list to find appropriate foods. If Weruva foods are sold in your country, they make a lot of low phosphorus foods (especially in North America) that are also low in carbs, with some not much higher in protein than a renal diet.

If your cat is in diabetic remission, it is very important to be careful about the carbs if switching to a low phosphorus diet. It’s possible a high carb renal wet food may not kick your cat out of remission, but the odds are not good, and they are probably worse for a renal dry food. It’s safe to stick to a low carb diet, hopefully one as low in phosphorus as you can get away with.

Many vets unfortunately are not supportive of feeding anything but a renal diet even to diabetic cats in remission. I don’t understand why vets would be so cavalier about risking a cat leaving remission just to feed a renal diet when there are alternative low phosphorus, low carb options to try. To a vet, maybe it’s just a simple equation: giving an insulin shot is just one extra thing, what’s the big deal if you need to start doing that again to feed a renal diet? But keeping a cat in remission seems like something I would fight hard to maintain – a real quality of life issue. Who wants to worry about hypos or trying to feed on a schedule? Not to mention poking your cat with a needle more than needed. Insulin for cats is not cheap, either. I’m not sure I believe that the supposed benefits of a renal diet are in any way worth risking remission especially in an early stage CKD cat, when the real benefit of a low protein diet is questionable anyway, even more so if you have a fairly low protein, low phosphorus, low carb diet available. (Not feeding a renal diet doesn’t mean you are going to feed a high protein diet!) In late stage CKD, when the Urea/BUN is often quite high, a low protein diet would offer more benefit.

FYI, diabetic prescription foods like Purina DM are not very low in phosphorus. E.g. Purina’s DM wet and dry foods are (as of 2020) almost 300 mg/100kcal – almost 3X higher in phosphorus than a renal prescription food.

And if you live outside of North America, note that some of the renal diets are much lower in carbs than the North American versions. Even Purina’s diet sold in Europe is lower in carbs / higher in fat. Some companies like Specific and Trovet (sold in Europe, maybe elsewhere) make low protein wet foods that are not that high in carbs and are low in protein (but very high fat – apparently the European vet community does not worry as much about fat causing pancreatitis in cats).

Dry food in general is highly discouraged for diabetic AND cats with CKD. Yes, some cats are dry food addicts – they have to eat. If you must, there are very few low carb foods out there that are suitable for diabetic cats. In North America, the two you’d choose would be Young Again LID Zero Mature Health (low in phosphorus). Second choice would be Dr. Elsey’s Chicken dry food (much higher in phosphorus). Both of these are very high in protein FYI. Wysong makes Epogen 90 which unfortunately is very high in phosphorus.

Although freeze dried raw would probably be low in carbs, most freeze dried raw foods are not low in phosphorus, and some are quite high.

What do I feed my IBD cat?

While feeding a low phosphorus diet to CKD cats is important, I would try hard to control a cat’s IBD if the cat has that too, obviously, and in most cases I’d prioritize the IBD. But it can be a juggling act. If your cat already had IBD before being diagnosed with CKD, start with what you know your cat can eat and can’t eat and aim for the lowest phosphorus foods that you can get away with that also satisfy the IBD issues in your cat. You may not have the luxury to worry about protein too. Your cat also has to like the food. Just do the best you can.

IBD can have different dietary triggers in different cats. Some IBD cats are allergic to specific proteins like chicken or beef. But if your cat is instead sensitive to some specific ingredient (e.g. guar gum), then there’s no point in avoiding foods with chicken. If your cat is sensitive to chicken or fish, that eliminates many low phosphorus choices, unfortunately. There just aren’t many “novel protein” based diets, e.g. with rabbit or venison, that are low in phosphorus. If need be, feed the lowest phosphorus food you can get away with and if it’s not very low, use a phosphorus binder if you must, if your cat’s blood phosphorus gets too high.

If you aren’t sure exactly what the cause of the IBD is, you can try prescription diets like Hill’s z/d. There are also brands that make limited ingredient diets like Hound & Gatos, Koha, Identity, Dr. Elsey’s, Rawz, most of which are not very low in phosphorus unfortunately. A few are not too high. Again…if one of these foods works great for IBD for your cat and it’s not low in phosphorus, maybe just use a phosphorus binder if needed in that case.

IBD is also a possible reason to consider making your own food (cooked or raw) as well. At least if you make your own food, you have complete control over the ingredients. There are balanced recipes that can be made low in phosphorus by avoiding bone in the food, and some “premix” completer supplements can be added to muscle meat e.g. chicken thighs (lower in protein than chicken breast), making it not hard to make your own balanced recipe, assuming the premix itself does not add much phosphorus.

What should I feed if my cat has signs possible of early CKD but has not yet been diagnosed?

There’s nothing wrong with feeding a low phosphorus, non-prescription diet to any mature cat, whether the cat has CKD or not. You can always do that “just in case,” but a reduced phosphorus diet may not prevent the onset of CKD. Improved hydration may help.

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Often it’s quite obvious that your cat has CKD: the cat has some symptoms, peeing and drinking more, reduced appetite etc…confirmed with elevated blood tests and urinalysis. Changing the diet is one of the most beneficial things you can do after your cat has been diagnosed.

But sometimes it’s not obvious that your cat has CKD – maybe there are no symptoms at all, no increased drinking or urination, no loss of appetite, etc. Maybe just an elevated Urea/BUN blood test or an elevated SDMA test, with everything else normal. Sometimes the elevated blood test is a hint that the cat is developing CKD (especially an older cat). Sometimes the elevated test might be a fluke or have some other explanation (especially in a younger cat less likely to develop CKD).

Should you change the diet? Is it really going to delay the onset of CKD? Actually, its not clear that diet will make any difference at this point. E.g. there’s no evidence that excess phosphorus or protein causes CKD, so it would stand to reason that reducing them won’t forestall CKD either.

The one thing I would focus on is improving hydration, especially if the cat is presently eating dry food. Wet food makes it much easier for cats to stay hydrated, and better hydration makes it easier for the kidneys to work. So switching a dry food-eating cat to wet (at least partially, ideally all wet) is probably a good idea, at least if the cat will eat wet food well enough to maintain weight. Don’t starve your cat and see her lose weight if she hates wet food…but if she will eat wet food, try switching away from dry.

And if you do feed wet food, try adding a few teaspoons of water to it if your cat will eat it that way.

A reduced phosphorus diet may not prevent a cat from getting CKD. On the other hand, there is no benefit to feeding a high phosphorus diet to an older cat anyway, and mature cats need little phosphorus in their diets. (Kittens need phosphorus to grow.) There is no reason not to feed a low phosphorus (not prescription) diet to a mature cat, whether the cat has CKD or not. E.g. if you feed Fancy Feast pate (high in phosphorus) to a 12 year old cat, all of the extra phosphorus is just washed out in the urine. If the cat winds up developing CKD, then you are ahead of the game by switching to a reduced phosphorus diet early.

Protein is different. Cats need protein as discussed above, and you don’t want to restrict it too much. Reducing the protein e.g. renal diet means increasing fat and/or carbs (renal diets are high in carbs). So switching a “pre-CKD” cat to a low protein diet (e.g. renal diet) might not be a great idea and may not be helpful anyway. Reduced protein reduces the Urea/BUN, but usually BUN is not very high even in early stage cats. There is no evidence that more protein causes the kidneys to “work harder” (in case you had the idea that a reduced protein diet makes it easier for the kidneys – not necessarily, especially if BUN is not very high). The main issue with dietary protein for CKD cats is high levels of Urea building up because the kidneys can’t filter it out well anymore. If Urea/BUN is normal but SDMA a tad high, what benefit is there from even lower BUN at this point? It’s not clear there is any benefit.

There are “early renal” diets that are low in phosphorus but a little higher in protein than “regular” renal diets, but even the early diets are higher in carbs and plant ingredients. And often the extra protein comes from a plant ingredient like potato protein. An “early renal” diet will be lower in phosphorus for sure and again, reducing phosphorus for any cat suspected of CKD soon is not a bad idea but not necessarily going to slow down progression to CKD.

E.g. if my cat is 12 and has an elevated SDMA but everything else is normal and no symptoms? If she eats dry food, I’ll try to switch her to wet if she will eat it or add some water to her wet food if she will eat it that way, maybe invest in a fountain or another water bowl, encourage more water intake. If she’s eating a high phosphorus diet like Blue Tastefuls or Fancy Feast pate, I’ll try to switch her to something lower like a Weruva food if she will eat it – don’t want her to lose weight either if she doesn’t like the new diet. Maybe I’ll look at adding some supplements like fish oil for the added omega fatty acids. But I’m probably not going to switch her to a renal diet.

Sometimes a younger cat (where CKD is much less common than in older cats) will have a slightly high Urea/BUN blood test and nothing else high, no symptoms etc. The high BUN may be caused by several things e.g. a high protein diet. (Raw diets for example tend to be very high in protein.) If the BUN is one point above the normal range, it may mean absolutely nothing. Re-test in a few weeks and it might be normal. If BUN is double normal range and everything else is normal? That’s different, maybe I’d want more testing – repeat the blood tests in a few weeks and if BUN is still really high, do more testing like getting an ultrasound. A renal diet will be low in protein so in theory would lower the BUN – but if this is a young cat, would you really want the cat eating a low protein renal diet the rest of his life? I wouldn’t if possible – I’d want to know why BUN is so high and that really means, because that’s unusual. If the current diet is very high in protein (see above to learn what “high protein” means in cat food – don’t just look at the percentages on the food label), you could try a reduced protein diet instead of switching to a low protein renal diet. It would seem that a very high BUN in a cat without other high tests or other issues indicates some other problem, not a problem with the diet.

What about dietary sodium?

A lot of what we know about feline CKD comes from our knowledge of human CKD, which has had vast research devoted to it. And conventional wisdom with human CKD tells us to limit sodium, since sodium can raise the blood pressure of humans, and high blood pressure is generally not good for the kidneys.

But, cats are not exactly the same as people, and one difference seems to be in regard to sodium. Turns out, according to studies, that dietary sodium does not seem to raise blood pressure in cats!

Further, here’s a fun fact: cats can drink salt water! Humans cannot (at least, not much). If you are stranded on a raft in the ocean with your cat, and you are thirsty, you had better hope it rains, but your cat can drink the sea water! You cannot. A cat’s kidneys can process the extra sodium – they have evolved to do that. Humans cannot.

So it stands to reason that dietary sodium would not affect cats the way it does humans either.

Despite this, many renal diets are actually severely sodium-restricted, and this may have no benefit at all for CKD cats – it may actually not be great for them. I don’t see any reason to feed a low sodium diet to a CKD cat. However, I would still avoid a high sodium diet, because the extra sodium still must be removed by their kidneys. (Some regular cat foods are really high in sodium – if the food list you consult includes sodium, pay attention to it.)

What about feeding food with fish?

I’ve read enough negative things about fish that I do not feed it to my young cats. You can do your own research on that. (Fish oil is something else – a good source of omega fatty acids, an ingredient I like in my cats’ food.) But, if my CKD cat is struggling to eat, of course I’ll feed fish if I have to. The primary goal is always to keep a CKD cat eating, especially one with a poor appetite. My CKD cat fortunately loved chicken, and there are many chicken-based foods, so I was able to avoid feeding her fish much at all until she declined in her final months. At that point, I did feed her fish sometimes to keep her eating.

The fact that a food has fish in it does not necessarily mean it is high in phosphorus or sodium. Don’t make assumptions about that – always check the manufacturer’s listed phosphorus and sodium content for any food. Fish foods can be high in iodine as well but again – not always. (High iodine diets may not be good for hyperthyroid cats.)

If you are worried about fish, at very least you can aim for a food that isn’t all fish – e.g. one that is “chicken and salmon” not just “salmon.” I think I’d prefer salmon to something like tuna, too – just assuming there is probably more mercury in tuna. But again…if my CKD cat is just not eating but loves food with some tuna in it, of course I’ll feed it to keep her eating.

Is a high fat diet bad for cats? Doesn’t it cause pancreatitis?

Don’t blindly believe what someone repeats to you about dietary fat and feline pancreatitis. Check out reputable articles online e.g. from Cornell and see what they have to say about feline pancreatitis. Avoiding high fat foods for your CKD cat may greatly reduce the number of low phosphorus food choices you have, since many are high in fat.

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The short answer is: there is no evidence that dietary fat causes pancreatitis in cats. In dogs, yes, there is some evidence. But cats are not dogs

Don’t believe me? Google the scholarly pages on “feline pancreatitis” and read the results from Cornell, VCA, etc. Which one mentions dietary fat as a confirmed cause? None that I could find. In fact, what you’ll find instead is that no one really know exactly what causes pancreatitis in cats.

The best you’ll find is: some vets and some cat experts believe dietary fat can cause pancreatitis in cats. Some of them just don’t know but are repeating the “fat causes pancreatitis” advice anyway…just in case?

This is one of those frustrating cases of “confirmation bias” and faux conventional wisdom being repeated authoritatively, as if it were fact. The next time someone tells you this, ask them, “Show me the proof! Where is the research?” If they refer you to an article about dogs, ask for one about cats. You’ll be waiting a long time.

Related to CKD, the reason you might have this question about fat is that many CKD-friendly foods that are moderately low in protein are quite high in fat. Some are well over 60% of calories from fat, which might seem frighteningly high at first glance if you grew up in the era of human dieting when fat was demonized as horrible for humans, and dietary fat reduced the quality of the food. Whether or not that is really still the conventional wisdom in human nutrition anymore, fat is quite natural and important in a cat’s natural diet. Many cats digest high levels of dietary fat quite well.

So if you believe the “fat causes pancreatitis!” myth, you may be afraid to feed a high fat diet, especially if you or your cat has had past experience with pancreatitis – it’s scary!

Keep in mind that there is a “cost” to a reduced fat diet: either higher carbs or higher protein (or both). All the calories in cat food come from protein, fat, and carbs. The total calories from all three is a closed circle – all add up to 100%. If I switch from a diet that’s 60% of calories from fat (so 40% from protein and carbs) to a diet that is only 25% of calories from fat, that means 75% of calories from protein and carbs…higher protein most likely, maybe carbs too. Higher protein (more than the cat needs to sustain muscle mass) means more Urea waste and a higher Urea/BUN test – not good for CKD cats especially in the later stages. A higher carb diet might be tolerated well by some cats, but is not natural for cats, and some cats don’t do well on the plant ingredients for one reason or another. A high carb diet can lead to diabetes in cats predisposed to be diabetic, too.

That doesn’t mean you should go ahead and keep feeding the current high fat diet to your cat if your cat happens to be doing poorly on that food. Of course, change the food if your cat isn’t doing well on it. But in general, a low fat diet is not beneficial to cats…and there’s no evidence it reduces the incidence of pancreatitis in cats. Yes, pancreatitis is scary and dangerous if untreated, and you may be tempted to do anything to try to avoid it in the future, but the main thing seems to be to keep the cat eating to get through it, not to switch to a low fat diet that could have other consequences. There’s nothing wrong with changing diets completely if you feel the cat was not doing well on the current diet…but the problem may have nothing to do with the fat in the food.

Is grain-free cat food really bad for cats – does it cause heart disease?

Many low phosphorus cat foods are “grain-free,” and some vets and others are starting to warn clients needlessly to avoid “grain-free” diets.

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“Grain-free food causes heart disease in cats!” is another myth based on a grain of truth (so to speak!), but the issue has been greatly distorted and misunderstood. Common sense should tell us that cats don’t need grain in their diets – they are meat eaters, obligate carnivores whose natural diet is birds and mice, not wheat and rice!

To start: the potential issue that some studies indicate that a diet high in lentils and/or peas (which can replace grains in some pet foods) can cause a type of heart disease called Dilated Cardiomyopathy (DCM) in dogs. And it appears the issue is not a lack of grain – it’s the inclusion of ingredients like lentils and/or peas causing a taurine deficiency (again, this has been observed in dogs!)

Is it possible this could be an issue for cats too? It can’t be completely ruled out…but again, remember that many “grain-free” diets don’t have lentils or peas in them. Some “grain-free” cat foods have no plant ingredients in them at all.

But if you are worried about this potential risk of DCM, look at the ingredients of your cat’s food. If the food is high in carbs – full of plant ingredients – and there are high levels of peas and/or lentils in the food (especially a dry food, not so much wet) – then avoid these foods. Still, unlike dog food, almost all cat food includes added taurine, something that hasn’t been done historically in dog food. (Cats cannot make their own taurine – an essential amino acid – and must get it from the food; dogs can make their own taurine.) So a taurine deficiency seems less likely than in dogs.

In any case, for those of us who believe a high carb diet is unhealthy for cats, it’s a moot point anyway, because we would avoid a high carb diet anyway, whether the plant ingredients that contribute the carbs are grains or not.

What if my CKD cat will eat only Fancy Feast or Friskies or something else “bad?”

Some cats are really picky…or they have become Fancy Feast or Friskies addicts. It may well be that if your cat gets kidney disease, he may not like any of the “better” low phosphorus diets. And he’s got to eat!

Unfortunately, most Fancy Feast and Friskies are not low in phosphorus, and some are quite high, especially the pates. The “gravy” foods are much lower in phosphorus but still not low. (There is ONE Friskies food that is fairly low in phosphorus – that’s it! There are few Fancy Feast gravy foods that are not too high, but, most especially, the pates are high in phosphorus – even the Fancy Feast “senior” foods!)

Some people seem not to realize that all cat foods have a different phosphorus content, and even their vet may pose the food choice as “feed renal foods – otherwise, just feed anything.” There are a lot of low phosphorus foods that aren’t “renal foods” that are much lower in phosphorus than Fancy Feast or Friskies. It’s well worth trying at least a few of those non-prescription foods before resorting to Fancy Feast or Friskies. Some cats who hate prescription diets may love low phosphorus Weruva foods. (And some cats hate Weruva too – every cat is different!)

You might be tempted to feed Fancy Feast because you think it is cheaper than some of the “kidney-friendly” foods – but if you look at the cost per calorie, Fancy Feast is really not that cheap! (Friskies is cheap – Fancy Feast really isn’t that cheap! But, Friskies is not exactly health food if you know what I mean.) Fancy Feast is cheaper than the renal prescription diets, but per-calorie, it’s about the same as some of the very low phosphorus, high calorie Weruva foods (if you get the larger cans – the tiny Weruva cans are much more expensive).

So I wouldn’t step right up to Fancy Feast just because your cat won’t eat renal foods or any of the lowest phosphorus Weruva foods. Work your way up if you can and try foods that are “not quite as low but lower than Fancy Feast.” For example:

Try foods below 100 mg/100kcal e.g. renal foods or Weruva Wx.

Cat won’t eat them? Try foods below 150 mg/100kcal in phosphorus.

Cat won’t eat any of them? Try foods below 200 mg/100kcal. Then try some below 250.

It’s up to you how many foods you want to try before giving up and just feeding Fancy Feast etc. But…you could try at least a few low phosphorus foods before giving up, if your cat won’t eat the renal diets.

Fancy Feast pate is anywhere from 300 to 400 mg/100kcal – so if you can get your cat to eat something half of that, that’s still a lot better than feeding just Fancy Feast, even if higher than a renal diet.

Maybe you’ve tried even some “not so high” phosphorus foods and your cat just won’t eat any of them but still loves Fancy Feast. It is really necessary to try dozens of different low phosphorus foods? Probably not. Try as many as you feel necessary…and if you have to feed Fancy Feast or Friskies to keep your cat eating? So be it. Add a phosphorus binder if your cat’s blood phosphorus gets too high.

Why is my CKD cat losing weight even though she is eating well?

There are a few possible reasons, but the first reason is probably the most obvious: because your cat isn’t eating enough calories a day. It’s calories you care about, not “ounces or grams of food!’ Every food has a different calorie content. A 5.5oz can of Weruva Classic Grandma’s Chicken Soup has only 106 calories in it. A 5.5oz can of Weruva BFF PLAY Chicken Checkmate has far more: 169. You can’t feed the same amount of either of those foods and expect your cat to get enough calories. (Why are the two foods so different? Because one has more moisture in it and/or has a higher protein / lower fat content than the other.)

Before considering other reasons, try to add up how many calories your cat eats now. The calorie content is given on the food label, in kcals. For wet food, the kcals (calories for our purposes) are given per the can or pouch. For dry food, they are usually given per cup. And both will list the Metabolizable Energy (ME) – usually kcal/kg (calories per kg), sometimes calories per oz.

Mature cats typically need to eat about 20 calories per pound per day (or about 45 calories per kg per day) just to maintain weight, sometimes more.

E.g. let’s say your 8lb cat is eating one 5.5oz can of Weruva BFF PLAY Chicken Checkmate every day. Weruva says there are 169 calories per 5.5oz can. That should be about enough. Some cats might need a little more.

But if you said your 8lb cat is eating maybe 3/4 of a can of Checkmate a day, that’s just not enough. He needs to eat more – maybe another food he likes better?

On the other hand, if you said he was eating two 5.5oz cans a day and STILL losing weight, that’s too much – then I would look for another cause like hyperthyroidism, IBD, or diabetes.

Adding up the calories for dry food might be a little more complicated but easy if you have a kitchen scale (and you have only one cat eating at the dry food bowl). Let’s say the bowl with dry food in it weighs 300 grams in the morning. Tomorrow morning you weigh it again and now it weighs 270 grams – so your cat ate 30 grams in the last 24 hours. On the side of the bag you see that the food has a Metabolizable Energy (ME) of 3,800 kcal/kg (same as 3.8 kcal per gram). So the number of calories is 3.8 x 30 grams = 114 calories. Maybe write down the weights three days in a row (noting the new weight if you re-fill the bowl) and average them. Maybe your cat eats 30 grams one day, 28 grams the next, 34 the next. So the average is 30.67 grams.

How do I get my cat to gain weight? What should I feed?

The first question to ask is, “Is my cat eating enough calories every day?” Every cat food has a different calorie content. Cats typically need to consume at least 20 calories per pound per day (45 calories per kg per day) just to maintain, sometimes more…and more calories than that to gain. The calorie content is given on the food label, in kcals.

So whether or not your cat “likes” the food…is he eating enough calories a day? If not he is not going to gain weight.

Obviously if he doesn’t seem to be eating enough or doesn’t like his food, you can try another food to try to find one he likes better. If you find he won’t eat even a “junk” food like Fancy Feast well…then maybe he’s got some other issue like nausea or dehydration. So you need to treat that first before worrying about the food. Some CKD cats would benefit from an appetite stimulant at some point, something your vet can prescribe.

But if he seems to like his food – if he’s eating enough calories and still losing? And you are offering him as much food as he wants? Then he might have some other issue like hyperthyroidism, diabetes, or IBD, especially if he has a ravenous appetite and is still losing weight.

Of course if your kitty needs to eat more calories and he would happily eat Fancy Feast or some other junk food well…then it’s a matter of trying to find a low phosphorus food he might like better than his current food (many cats hate the renal diets). Most “junk” foods like Fancy Feast are high in phosphorus, unfortunately. But there are quite a few “non-renal” foods that are low in phosphorus. Ideally you would also feed a calorie-dense food that is high in fat.

Sometimes you have to feed a higher phosphorus diet like Fancy Feast to get your cat to eat well. But it should be a last resort, not a first choice. Many people seem to revert to feeding any high phosphorus food their cat will eat if she won’t eat the renal diets (many cats don’t like them), but there are quite a lot of non-prescription low phosphorus foods (especially in North America) to try in between.

One food that’s helpful to have on hand is a “recovery” food like the Hill’s a/d Urgent Care food. It is very calorie-dense and rich in nutrients. It’s not low in phosphorus (the Royal Canin recovery food is even higher), but sometimes you don’t have the luxury to worry about the phosphorus. The recovery food is not really great to feed as the only food long-term, since it’s not designed to be fed that way – but if your cat has crashed or suffered some kind of trauma and you are trying to bring her back, the recovery foods are a good food to consider. (Hill’s a/d is mushy so easy to syringe as well if you have to syringe feed.) But you will need a prescription in North America for one of the “recovery” foods. Hopefully a vet will be supportive.

Read the other questions for info on other types of food and supplements you might be considering, e.g. kitten food and high calorie gels and why they may not be your best choice.

What about “high calorie gel” supplements?

There are a number of “high calorie supplements” out there. They are all high in fat. I would use them sparingly and not use one until you’ve tried to get your cat to eat enough calories from a complete/balanced cat food first. (And at worst, try a nutrient-dense recovery food like Hill’s a/d Urgent Care, a prescription food in North America.)

The main thing is, you don’t want to replace too many calories of balanced cat food with pure fat. If the choice is between your cat eating only half a can of food at the moment and also eating some of the high calorie gel or just the half can? I’d add the gel in that case. But if the gel reduces the cat’s appetite for balanced cat food, it’s might not be helping and could be hurting.

Don’t use a calorie gel if your cat will eat some other balanced cat food well and get enough calories from that alone. Some people seem to think the renal diets that so many cats hate are the only acceptable food choice for CKD cats, and if their cat won’t eat enough of them, adding a “calorie booster gel” is their next best choice. It would be healthier just to feed a balanced cat food instead if your cat would eat one.

Be especially careful adding a high fat gel to a renal food that is already low in protein. Adding more fat to an already low protein food may reduce the amount of protein your cat ingests even more…the last thing you want to give to a cat who may already be losing muscle mass.

Some people use rendered duck fat as a natural high calorie supplement. It is extremely calorie-dense, so the same applies: use sparingly! You might do best adding some duck fat to a high protein, not-high-fat food instead of adding it to a food that’s already high in fat.

Does feeding cooked egg white help a cat maintain/gain weight and muscle mass?

Cooked egg white is a very pure, low phosphorus source of protein for cats, with a high bioavailability, meaning it is extremely well absorbed during digestion. Some people add cooked egg white powder (don’t use raw egg white) to boost the protein in their cat’s diet. Egg white has very little phosphorus in it, so that’s excellent for a CKD cat.

Unfortunately, egg white powder is not very calorie-dense. So you’d need to add a lot of it to really boost calories much. And even though it’s a high quality protein, more protein from egg white still results in more Urea waste. So there is a limited upside.

If you were thinking about adding egg white to a low protein renal food…consider that the Weruva Wx Phosphorus-Focused foods already use egg white in their foods, for exactly this purpose: protein boost without much added phosphorus. It might be easier just to feed Weruva Wx instead of a renal diet in that case, if Weruva Wx is available where you live and your cat likes it.

What if my cat gained weight and improved after diet change, but creatinine and BUN went up?

Creatinine and Urea (BUN) are waste products that the kidneys normally remove (mostly). We run blood tests for them to see how much the kidneys can remove, to see how well the kidneys are working. When creatinine and BUN (Urea) blood tests go up go up, usually that means kidney function has declined. But in some cases it can simply mean that the body is making more of those waste products now than the last time the blood tests were run.

Details:

Creatinine is a waste product from the normal breakdown of muscle. A cat who has lost a lot of muscle mass (unfortunately quite common with CKD cats) will have a reduced creatinine just because of the lost muscle. But what if a cat who had lost a lot of muscle gains some back e.g. after a diet change? Then the creatinine will go up. Some people automatically think, “OMG, higher creatinine, isn’t that terrible???” But that’s not a bad thing at all in the case where the cat has gained muscle! It just means there is more creatinine waste building up than before due to increased muscle mass.

Gaining a few ounces probably won’t affect the creatinine much, but gaining a few pounds probably will (assume some of that is muscle, not just fat or retained water or something). In that case, at least some increase in creatinine would be expected – and the weight gain in a thin CKD cat is something to celebrate. CKD cats who gain significant weight and seem to be improving probably aren’t about to pass away.

Similarly, Urea (BUN) is a waste product largely from the breakdown of dietary protein. While very high Urea levels are not good for the body, a modest increase due to a higher protein diet might be worth it if it helps the cat gain weight back or keep it

A common example is a cat who had been barely eating a low protein renal diet and lost weight (and presumably muscle) on it…then was switched to Weruva Wx (which is extremely low in phosphorus like a renal diet, but is fairly high in protein, unlike a renal diet) and the cat liked this food better, ate more, and gained significant weight. So in that case, both Urea/BUN and creatinine would be expected to go up. (If you re-tested phosphorus and that is still low, that’s another indication the kidneys have probably not declined.)

Some vets seem to panic when this increase in creatinine and Urea/BUN happen after a diet change and urge you to switch to a lower protein renal diet, but if the cat has gained significant weight and is doing better, why would you want to change anything, just because a few blood tests went up? It’s important to understand what the tests mean in context.

What if my CKD cat just won’t eat ANYTHING at the moment?

There may come a time when your cat’s appetite is awful and she may not want to eat anything. Be very careful. Unlike other mammals, cats can’t go that long without eating something, or they could develop a dangerous condition called Hepatic Lipidosis (“fatty liver”). If your cat hasn’t eaten anything in a few days, it’s important to start syringe feeding if you can’t get her to eat any other way.

Meantime, pull out all the stops to get your cat to eat. Try anything meat-based to get your cat to eat something: Fancy Feast, dry food, tuna, meat-based baby food (no garlic or onion), cooked meat, even Temptations Treats. (Temptations treats are not low in phosphorus or very healthy, but some are balanced, surprisingly – check the label.) Sometimes, eating anything is a lot better than eating nothing, even if the food is not great for the kidneys. It’s a lot worse for the cat to get fatty liver.

Keep in mind that many CKD cats can get nauseated and not want to eat anything. If you try your cat’s old favorite food from before CKD diagnosis and she still won’t eat it…that’s a sign that she truly has no appetite. But if she won’t eat her renal food but will happily gobble up Fancy Feast…that’s different. Try another food!

Otherwise, look into treatments for nausea. There are prescription meds like Zofran (Ondansetron) and Cerenia (which is really an anti-vomiting med which can help with nausea). But you could try a small dose of famotidine (Pepcid AC), which you can buy over-the-counter in North America – e.g. 1/4 of a 10mg tablet so 2.5mg every few days or sometimes daily. Check with your vet!

If your cat happens to be constipated, you need to address that! That can really affect appetite too. (Miralax is a common, effective remedy. Ask your vet!)

Some cats would benefit from an appetite stimulant like mirtazapine or cyproheptadine, but if your cat is suffering from nausea, you need to address that first! If you’ve ever been nauseated, you can imagine that taking a drug that makes you want to eat more might not work very well in that situation. I would use an appetite stimulant if you need one but would first try the the other things.

CKD cats can easily get dehydrated as well, so some of the things that would help them stay hydrated e.g. SubQ fluids might help appetite too, since a cat that feels lethargic from dehydration may have a poor appetite, too.

Note that cats who have become lethargic and have zero appetite could have developed pancreatitis, which is very dangerous, not something to fool around with. Your vet can run a blood test to try to confirm or do an ultrasound. Pancreatitis is not uncommon in CKD cats unfortunately and could end your cat’s life more quickly than CKD could.

Can I feed my other non-CKD cats the same food?

You can feed any mature cat a low phosphorus (non-prescription) diet. Mature cats need very little phosphorus in their diets, and most cat foods have far more than they require anyway. Kittens are different: they need phosphorus to grow! So, don’t feed them a low phosphorus diet or not without also feeding them something else with more phosphorus in it.

However, I wouldn’t feed to mature cats without CKD the renal diets, which are very low in both phosphorus and protein. (It’s OK if they eat some renal food, just not as their primary diets.) While a healthy mature cat might do OK eating a renal diet, it seems not worth the risk of malnutrition or becoming obese or diabetic (since renal diets are in general very high in carbs).

A few “non-renal” foods like Weruva Wx and Dave’s are also possibly too low in phosphorus for cats without CKD, though again it’s possible a cat without CKD might do OK on them. (Dave’s restricted phosphorus is very low in protein and high in carbs, like the renal diets; Weruva Wx is low in carbs and has plenty of protein for any cat.) If you look at the nutrient profile for adult cats from AAFCO, the minimum phosphorus is 0.5% DMB, and the Weruva Wx and Dave’s are both below that. However, the FEDIAF (European pet food nutrient regulator) has a lower minimum phosphorus requirement than AAFCO. Weruva Wx and Dave’s would barely meet the FEDIAF requirement for adult cats, so it’s possible a cat would do OK.

However, it is possible for a cat’s blood phosphorus go to too low, so be careful about that. If you decide to feed very low phosphorus diets (foods that don’t meet the AAFCO nutrient profile – almost every non-renal food meets AAFCO except the few noted above) to a non-CKD cat, I would get regular phosphorus blood tests to make sure the phosphorus remains in range. You don’t need to worry about this with “regular” cat foods – e.g. all Weruva except Weruva Wx meet the AAFCO nutrient profile.

What if i choose to do nothing special and just feed my CKD cat whatever she wants – is it really going to matter in the end?

Some people have the philosophy of, “I’m just going to let my cat eat what she wants and let her be happy – and if she doesn’t live as long, that’s OK, at least she enjoyed her life.” And hey, in some cases, diet for CKD cats might not matter much in the end. Every cat is different. I have heard of people feeding Fancy Feast to their CKD cat who wound up living for years. I’ve also heard of cats who were fed renal diets exactly as the vet recommended yet who wound up living only a short time anyway. You just never know.

In some cats it may matter a lot. But how can you ever really tell what would have happened had you fed something else for a year? Kitty health is pretty complex even if it might seem cut-and-dried sometimes. It’s hard to say, “If only I had fed a low phosphorus diet the last few years…maybe my cat would have lived longer?” Who knows?

But we do know that on average, feeding a low phosphorus diet should help most CKD cats. If you feed a high phosphorus diet and your cat’s blood phosphorus starts going way up, that is not something that will have no consequence. It will eventually make your cat feel awful. You could add a phosphorus binder to the food – some cats do well on the binders, but they aren’t perfect. They don’t remove all of the phosphorus from the food, and they can cause side effects like constipation.

A high protein diet might cause your CKD cat’s Urea/BUN to go really high (especially in the later stages) as waste products build up and cause problems in the body and shorten the cat’s life. Dry food makes it harder for a CKD cat who has to drink lots of extra water anyway to stay hydrated.

I would argue that for many people, it’s not hard to try a few low phosphorus foods, so why not try a few – what if you find a low phosphorus food your cat loves as much as Fancy Feast? Why wouldn’t you feed it? It’s true that some people live in parts of the world with limited access to cat foods that are low in phosphorus, but many people in the US live close to a Petco or Petsmart with a variety of low phosphorus foods available. So it’s easy to find a few foods to try. If you try a half dozen foods and your cat rejects all of them, you can always go back to Fancy Feast.

Some people think that these “special” foods are too expensive and not worth it. But some low phosphorus foods are very affordable. Some of the Weruva foods are very expensive and not high in calories, but other Weruva foods (the BFF PLAY and BFF OMG lines) are very calorie-dense and affordable in the 5.5oz cans, about the same cost as Fancy Feast per calorie. Most Friskies foods are high in phosphorus, but there is one Friskies gravy food (on food lists) that is low in phosphorus. Friskies is not a high-quality food, but for some, this one low phosphorus food might be no worse than what they are already feeding.

If you can get your cat to eat the lower phosphorus foods at least for a while, you might be able to put off the need for a binder a bit longer.

What if my cat loves high phosphorus wet food like Fancy Feast, won’t eat any low phosphorus wet foods…but loves renal (low phosphorus) dry food?

Fancy Feast (especially pates) are high in phosphorus so not great for CKD cats. Dry food, even renal food, has almost no moisture in it. Which is better, if your cat refuses to eat any other wet food but stuff high in phosphorus – should you risk high phosphorus with Fancy Feast or dehydration with the dry food?

I think I’d compromise and feed a little of both – and if your cat doesn’t mind water added to the wet food (some cats love it, some hate it), maybe feed some wet food with a lot of extra water to help compensate for lack of water in the dry food. You could mix the wet and dry together with water added.

You could always add a phosphorus binder (removes some phosphorus from the food before absorbed) to the Fancy Feast if your cat’s blood phosphorus goes too high – and binders work well for many cats, but they can cause side effects like constipation. And some cats reject food with binder mixed into it. And binders don’t bind out all of the phosphorus – maybe half at best?

You could try to help with dehydration with SubQ fluids or hydration supplements like Purina Hydra Care, but it would be easier for your cat just to get more moisture from her food, of course.

What is dry matter basis? Why does it apply to wet food?

Please read this article to read more about dry matter basis and percentages.

What is guaranteed analysis? What is typical analysis?

Please read this article to read more about guaranteed analysis vs. typical analysis.

Are there other good resources for learning about CKD?

Tanya’s Comprehensive Guide to Feline Chronic Kidney In-depth guide to Feline CKD created over 20 years ago by Helen Fitzsimons (Tanya was one of her beloved cats.) Includes detailed explanations about many topics related to CKD and numerous citations to research and articles. Probably more than you want to know about CKD. The site can be overwhelming if you are new to CKD – pace yourself! Come back to it when you have specific questions.

Dr. Ron Hines’s Vetspace : great articles about all things related to cats (and other pets), including detailed explanations about what various blood tests mean.

Feline Chronic Kidney Disease Facebook Support Group Very active Facebook support group for CKD cats created by Nancy Wizner. I have been an admin in the group since 2018.

Calcium Phosphorus Balance in Dogs and Cats – Wendy Brooks, DVM, DABVP Terrific article explaining why excess phosphorus in the diet is so bad for CKD cats.

Urea is truly toxic: the empire strikes back – by Lau WL, Vaziri ND A fairly concise explanation about why the main waste product of digesting protein, urea, is not good for humans (and so probably not good for cats, either).