WHAT TO FEED, AND WHAT TO AVOID

Royal Canin offers a renal palatability pack containing a mix of dry and wet kidney foods so you can see which flavours your cat prefers. This may be available from your vet, and is available online from Animed Direct.

Vetsend sells a taster pack including foods from a number of different brands.

Zooplus sells a trial pack of Beaphar renal diet foods.

Zooplus allows you to check the composition of many cat foods, both therapeutic and non-therapeutic.

So when should you start such a diet? Treatment recommendations for CKD in cats (2019) International Renal Interest Society divides CKD into stages (see How Bad is It?) and suggests starting a veterinary diet in Stage 2, i.e. when the cat's creatinine is over 1.6 mg/dl or 140 µmol/L. However for cats with proteinuria, it states "feed a renal clinical diet" regardless of the stage the cat is in. It also says that introducing a therapeutic diet "may be accomplished more easily early in the course of CKD, before inappetence develops."

The study that most experts cite when recommending a therapeutic kidney diet is Clinical evaluation of dietary modification for treatment of spontaneous chronic kidney disease in cats (2006) Ross SJ, Osborne CA, Kirk CA, Lowry SR, Koehler LA, Polzin DJ Journal of the American Veterinary Medical Association 229(6) pp949-57. This study found that feeding a therapeutic kidney diet helped to keep BUN levels lower and appeared to help prevent metabolic acidosis in cats with more advanced CKD. The study concluded "The renal diet evaluated in this study [Hill's k/d] was superior to an adult maintenance diet in minimizing uremic episodes and renal-related deaths in cats with spontaneous stage 2 or 3 CKD." By Stages 2 and 3, they are referring to cats with creatinine between 2.1 and 4.5 mg/dl (165 - 400 µmol/L international).

So if your cat's creatinine is over 1.6 mg/dl or 140 µmol/L and your cat is eating and not in crisis (e.g. just returned home from a stay at the vet's), I would consider starting a therapeutic kidney diet. If your cat's creatinine is below this level but your cat is stable, I would introduce these foods, especially if your cat has proteinuria, so you know which of them most appeals to your cat, but I would not feed them exclusively (see below).

On the other hand, if your cat is underweight or has a very poor appetite, or is recovering from a crisis, I would wait a while — Cats Exclusive Veterinary Center states that it is better not to feed therapeutic kidney diets to thin cats or cats with poor appetites. You should always address possible causes of inappetence, such as nausea or anaemia, before trying to persuade your cat to eat a therapeutic kidney diet.

How to Introduce a Therapeutic Kidney Diet

Instead, take steps to control any issues which may be causing your cat to feel sick or have no appetite (see Index of Symptoms and Treatments) before trying to introduce a therapeutic diet — the cat may associate feeling sick with the food and refuse to eat it at all; whereas if you had waited until the cat felt a little better, you might have been more successful. This is particularly important if your cat is diagnosed following a crisis and is still under the weather. 11 guidelines for conservatively treating chronic kidney disease (2007) Polzin D Veterinary Medicine December 2007 says "Force-feeding new diets, exposing patients to new diets while hospitalized, or administering medications or other unpleasant events during and around feeding times should all be avoided. A renal diet should be introduced to patients gradually."

Diagnostic and therapeutic approach to the anorectic cat (2001) Marks S World Small Animal Veterinary Association World Congress 2001 says that it is also better for cats not to introduce any food too quickly because cats are creatures of habit when it comes to food, so introducing it suddenly may reduce your chances of success.

Some cats do actually like therapeutic kidney diets (ironically, they are often other family cats who are healthy and do not need them!). If you happen to have a cat who likes the therapeutic diet, it is still better not to try to switch your cat over in one fell swoop, because a sudden change of food may cause diarrhoea.

Instead, mix a little of the new food with your cat's favourite food to start with, and gradually increase the proportion of the new food, over a period of several days or even weeks. There is no need to rush the introduction of any new food, therapeutic or otherwise, go at your cat's pace. Dietary considerations in dogs and cats with kidney disease (2008) is a video presentation by Dr CL Langston which says you can take as long as 4-6 weeks to introduce a therapeutic diet if necessary. Therapeutic kidney diets can be rather dry (even the canned food varieties), so it may also help to start with to put a little tuna water (the water in which tuna is packed) on the food to moisten it and make it taste a little better. You could also try warming the food. Some people have found puréeing the canned food makes it more attractive to their cats.

Your vet should advise you how much of a particular food your cat needs. You can also look at the brand's website (there are links here to the various brands) to see how much they recommend, and read here about calorie needs.

Acceptance and effects of a therapeutic renal food in pet cats with chronic kidney disease (2015) Fritsch DA & Jewell DE Veterinary Record Open 2(2) is a study by Hill's in which 94% of the cats were successfully transitioned to a dry therapeutic kidney diet.

You CAN change a cat's diet (2015) is a video with a tip by Dr D Chew on how to change a cat's diet which he states has never failed him yet.

Hill's has tips on changing your cat's diet.

Monitoring Cats on a Therapeutic Kidney Diet

Once you have begun a therapeutic kidney diet, you need to monitor your cat's weight and muscle status. I would weigh your cat at least once a week (you can find sources for suitable scales here) and also check his or her body condition score. The World Small Animal Veterinary Association has a Body Condition diagram showing how to gauge your cat's physical condition.

Prolonging life and kidney function (2009) Chew DJ & DiBartola SP CVC in Kansas City Proceedings states "Maintenance of stable body weight and serum albumin concentration suggests adequate intake of calories and protein whereas progressive declines in body weight and serum albumin concentration suggest malnutrition or progression of disease and are indications to increase the amount of protein fed."

If you notice any weight loss or if your cat seems less muscular, first make sure your cat is definitely eating the food, and eating enough of it — calories and total food intake also matter. If s/he is definitely eating the food, you could speak to your vet about topping up the therapeutic diet with additional high quality protein, such as egg whites. See Persuading Your Cat to Eat for ways to get additional nourishment into your cat.

If your cat continues to lose weight, speak to your vet about what to do. It may be that your cat would do better on another therapeutic kidney food, or may actually need another food, either instead of or in conjunction with the therapeutic kidney diet. Feeding cats with different nutritional needs: a dilemma in the multicat household (2012) Dr M Scherk Presentation to the 73rd SCIVAC International Congress 2012 says on page 425 "Just because someone has a specific illness does not automatically mean that the diet designed for that condition is the best diet for that individual. Every time we send home a therapeutic diet, we are performing a feeding trial with one subject in it (n=1). We have to get the cat back into the clinic and see how he/she is doing on that food. How is his weight? Increased? Decreased? How is his coat? Does he eat with enjoyment or vigour? What are his stools like (moist logs or dry pellets, cow patties or coloured water)? How energetic is he?...If his weight has decreased, is it because he isn't eating enough of the food we are giving him or is it because we aren't giving him enough of it? OR (and only once we have asked the previous questions can we consider this) is it because his illness has progressed or another illness has arisen." The article includes a very useful algorithm for what to consider if a CKD cat is losing weight.

Chronic kidney disease — feline (2010) Polzin DJ Nestlé Purina PetCare Handbook of Canine and Feline Clinical Nutrition pp84-89 has an algorithm on page 89 about when and how to feed a therapeutic kidney diet.

When a Cat Refuses a Therapeutic Kidney Diet

Firstly, don't try to introduce such a food when your cat is sick or not eating any food voluntarily — see above for more about this. When Thomas was seriously ill after initial diagnosis and returned home after four days on intravenous fluids (he also had anaemia, which can cause severe loss of appetite), we fed him whatever he would eat, and then tried to provide a more suitable diet once he was stable.

Also try a different therapeutic food — some cats love one brand, but hate the others. You can find lists above of the various US therapeutic kidney diets and UK therapeutic kidney diets. Many vets can give or sell you one can of various varieties, so you can try to find one your cat likes. You can also find retailers who will sell individual cans here.

Another solution is to mix the therapeutic food with the lowest phosphorus food your cat will eat, or to add a topping of something tempting (see above and Persuading Your Cat to Eat).

If you absolutely cannot persuade your cat to eat any of these foods, please do not feel too despondent. Although the evidence for feeding a therapeutic kidney diet is strong, it is more important that a cat eats than that s/he eats nothing. Don't forget, cats with creatinine below 1.6 mg/dl or 140 µmol/L probably do not need a therapeutic kidney diet yet — The Merck Veterinary Manual states "Animals in this stage [IRIS Stages 1 and 2] should be fed standard, commercially available maintenance diets, unless they are markedly proteinuric."

Even if your cat has more advanced CKD, starvation is far more life-threatening. Cats eat to live rather than live to eat, and if they do not like what is offered, they may simply refuse point blank to eat. This lack of food intake is particularly worrying with cats, because cats who do not eat may develop a condition called hepatic lipidosis (fatty liver disease) where the liver starts to function abnormally. Feline hepatic lipidosis: therapeutic considerations (2011) Armstrong PJ Presentation to the 36th World Small Animal Veterinary Association World Congress mentions that hepatic lipidosis can develop after only 2-7 days of not eating; and it can be life-threatening. Even if the cat does not develop hepatic lipidosis, not eating can be a risk. Nutritional management of renal disease (2008) Sturgess K Presentation to the World Small Animal Veterinary Association World Congress says "It is vital that the cat eats something, as body protein catabolism will have more serious adverse effect on CRD than almost any diet."

The kidney patient: what's for dinner? (2010) Francey T Presentation to the World Small Animal Veterinary Association World Congress states "By individual coaching most dogs and cats can be switched to renal diets and it is important to realize that this change should be made slowly over weeks to months if necessary. In advanced CKD, dietary changes are certainly more difficult and affected animals are less likely to accept diets to which they have not been used. Feeding these animals necessitates either a compromise with more palatable (and less optimal) diets or the use of assisted feeding strategies including feeding tubes."

ISFM consensus guidelines on the diagnosis and management of feline chronic kidney disease (2016) Sparkes AH, Caney S, Chalhoub S, Elliott J, Finch N, Gajanayake I, Langston C, Lefebvre H, White J & Quimby J Journal of Feline Medicine & Surgery 18 pp219-239 state "maintaining calorie intake is the highest priority in CKD and the preferred choice of diet is generally in the following order: wet renal > dry renal > home-prepared renal diet > wet senior > dry senior > wet maintenance > dry maintenance. Senior diets generally have lower protein (and phosphate) than adult maintenance diets but, in the absence of a renal diet, earlier intervention with a phosphate binder may be necessary.”

So don't beat yourself up if, after trying your best to get your stable cat on a therapeutic kidney diet, over a period of several weeks if necessary, you simply cannot persuade him or her to eat these foods. You do have to consider your cat's quality of life: would you want to spend the rest of your life eating a food you detest? Feeding cats with different nutritional needs: a dilemma in the multicat household (2012) Scherk  M Presentation to the 73rd SCIVAC International Congress 2012 says on page 425 "for well-being, the patient should enjoy the diet offered, regardless of what illness he/she has. It is always more important that they eat, rather than what they eat."

If necessary, aim for a compromise. You may be able to persuade your cat to eat a food that s/he enjoys that may replicate at least some of the benefits of these foods. Clinical evaluation of dietary modification for treatment of spontaneous chronic kidney disease in cats (2006) Ross SJ, Osborne CA, Kirk CA, Lowry SR, Koehler LA, Polzin DJ Journal of the American Veterinary Medical Association 229(6) pp949-57 is the study with the strongest evidence for therapeutic kidney diets, yet even that states "These findings emphasize the value of considering individual dietary components in the overall assessment of the benefits of dietary therapy. Individually or in combination, similar dietary modifications in the present  study may have minimized the number of uremic crises and mortality rate." See below for tips on choosing a non-therapeutic diet.

Therapeutic Kidney Diet Issues

If you purchase a US therapeutic kidney diet, you may note that the packaging says that you are not supposed to feed these diets for longer than six months, or that they are for supplementary or intermittent feeding only. This is because under AAFCO rules these diets are not a complete and balanced diet for a healthy adult cat - this is deliberate, otherwise they would not have their therapeutic qualities, such as low phosphorus levels. Pet Diets explains more about this (search for "supplemental or intermittent feeding" and one of the responses addresses this issue), and states that it is normally in order to feed these foods on an ongoing basis to CKD cats.

Most therapeutic kidney diets contain potassium in the form of potassium citrate. This is a potential concern if you are using an aluminium-based phosphorus binder, because products containing citrate may increase the absorption of aluminium. In practice, most people using therapeutic kidney diets will not also need to use a phosphorus binder; but if you need to use both, check Phosphorus Binders for possible solutions to this problem.

It seems that many vets suggest that it is acceptable to feed a therapeutic kidney diet to other family cats. I do not understand this. If the food is so potent that it is usually available by prescription only, how would it miraculously have no effect on other, healthy cats? The answer is that it will have an effect: non-CKD cats fed a therapeutic kidney diet for any length of time run the risk of malnutrition, particularly young cats and kittens, because of the reduced protein content of such foods. In a study into the use of a new phosphorus binder which was given to healthy cats, Efficacy and acceptability of the new oral phosphate binder Lenziaren in healthy cats fed a standard diet (2014) King JN, Erasmus HL, , Delport PC, Bester ICJ & Seewald W BMC Veterinary Research 10 258, a therapeutic kidney diet was also fed and the study states "the choice of baseline in the statistical analyses including group F (renal diet) was challenging due to the unexpected loss of body weight in the renal diet group, which was most pronounced in the acclimatization period."

Even for an older cat, it may not be wise to feed a lower protein diet if the cat is basically healthy.  Feeding the older cat to optimize health and longevity (2003) Freeman LM A Presentation to the Waltham Feline Medicine Symposium  states "some nutritionists actually recommend that older cats eat a higher protein level than younger cats. The jury is still out but for older cats without significant kidney disease, it is wise to avoid low protein diets unless there is a specific indication such as severe renal or hepatic disease."

Feeding cats with different nutritional needs: a dilemma in the multicat household (2012) Scherk M Presentation to the 73rd SCIVAC International Congress 2012 pp421-430 is an excellent article about how to feed family cats with differing needs.

Meow Space sell systems that permit only one cat to eat a particular food.

Sure Pet is a pet feeder system that works if a cat is microchipped, though it also comes with a microchip that you can attach to your cat's collar if necessary. It is  a British product, available directly from the manufacturer in a number of different countries. One model is also available from Amazon UK and Amazon USA. You can also buy collars with RFID chips which act in a similar way.

Non-Therapeutic Diets: Commercial Foods or a Homemade Diet

If you are unable to persuade your cat to eat a therapeutic kidney diet, you will have to consider feeding other foods instead. Although therapeutic kidney diets are often the ideal (see above), keeping weight on and your cat eating regularly are more important. The main options are non-therapeutic commercial foods or a homemade diet.

Do not introduce any new food suddenly, follow the guidelines for introducing therapeutic diets.

Commercial Foods

Commercial Non-Therapeutic Food: Composition

When choosing a non-therapeutic diet, as far as possible you want to replicate the benefits of a therapeutic kidney diet. Unfortunately it is not known exactly what is in the therapeutic kidney diets that makes them so effective, and these foods themselves vary in their composition. You can read more about their main features above.

Low Phosphorus

Even if you do nothing else, aim to feed a food as low in phosphorus as you can. See the Phosphorus page for more information on why this is so important.

Ideally, as mentioned by Dr Scott Brown in Management of feline chronic renal failure (1998) Waltham Focus 8(3), you want your cat to eat food with less than 0.5% phosphorus on a dry matter analysis (DMA) basis. In practice, you are unlikely to find any complete adult cat foods in the USA with a phosphorus level lower than 0.5% because that is the minimum phosphorus level required by AAFCO.

Chronic kidney disease (CKD) in dogs and cats — staging and management strategies (2015) A Presentation to the Virginia Veterinary Medical Association 2015 Virginia Veterinary Conference, Dr D Chew has a very useful algorithm on how to control phosphorus levels via food and phosphorus binders.

If you think you have found a food which is low in phosphorus, please be sure that you are looking at it on a dry matter analysis basis (DMA) basis. The labels on cans usually do not provide information on a DMA basis, so that apparently low level of phosphorus is unfortunately unlikely to be accurate. For this reason I have created tables of many US foods showing their phosphorus levels (see below).

High Quality Protein

During the breakdown of dietary protein in the digestive process, waste substances are created which are filtered out of the blood by the kidneys and excreted via urination. This is sometimes referred to as the removal of nitrogenous wastes. Unfortunately damaged kidneys find it harder to do this, which is why blood urea nitrogen (BUN) levels rise in CKD.

Therefore the goal is to feed a protein with the correct balance of amino acids to provide the cat with the ability to maintain and repair bodily tissues but in a form which needs as little breaking down as possible. That is what we mean in this context by "high quality protein." Proteins of this nature are sometimes referred to as having a "high biologic value." The food with the highest biologic value is actually eggs.

To replicate higher levels of B vitamins and essential fatty acids, you can try adding supplements to your cat's food.

Not all CKD cats need additional potassium but if yours does, your vet can recommend a potassium supplement. Many people are not too concerned about sodium levels, but if for some reason you are, the food data tables (see below) do include sodium information.

Interpreting pet food labels Dzanis DA US Food and Drug Administration has some information on interpreting cat food labels which may help you to choose a good quality food.

Interpreting food labels USA (2020) World Small Animal Veterinary Association explains what US food labels tell you.

Interpreting food labels EU (2020) World Small Animal Veterinary Association explains what European food labels tell you.

Pet food myth busters: answering common questions owners ask about pet food (2015) LM Freeman NAVC/WVC Symposia Proceedings has a good overview of pet food issues.

Advising pet owners on nutritional adequacy (2020) Lindner DE Clinician's Brief June 2020 pp12-16 discusses how to assess foods.

PetCoach explains more about the guidelines of AAFPO (Association of American Feed Control Officials). Note that the amounts given here are minimums.

Premium, Natural and Human Grade Foods

• Premium foods

• Natural foods

• Human grade foods

Premium Foods

People often assume that I feed so-called premium foods. However, I am not a fan of most premium foods: they often contain fruits and vegetables including cranberries, inappropriate for CKD cats, and in my opinion are unnecessarily complicated foods. Many of these foods seem to me to be designed to appeal to the humans buying them, not to the cat.

The Association of American Feed Controls Officials has stated "Because cats and dogs do not select their own foods, and their human owners do, it is not rare at all that labeling and marketing information is designed to appeal to the latest trend in marketing human products."

Cats have very little need for fruits and vegetables - normally they would only eat the small amounts contained in a mouse's stomach, and even those would be pre-digested by the mouse - so I do not see the attraction of all those carrots, sweet potatoes and blueberries for my cats. Some of these foods are also acidified — many commercial foods are, unfortunately, but again this is not suitable for a CKD cat.

Pet food myth busters: answering common questions owners ask about pet food (2015) LM Freeman NAVC/WVC Symposia Proceedings says "Pets require nutrients, not ingredients. A food full of great-sounding ingredients can be less nutritious than one containing less appealing (to people) ingredients. Some manufacturers may add ingredients to products solely for marketing purposes, to increase the appeal of the food to consumers. These ingredients may have unproven benefits, be present in miniscule amounts, and provide nothing to the food but added expense. More ingredients also mean increased quality control measures (and more time and expense) are necessary to ensure that the finished product adheres to the desired nutrient formulation."

If you do decide to feed this type of food (and I know some cats do enjoy them) and you are in the USA, check the food data tables to find those with the lowest phosphorus levels. If you can't afford such foods, don't worry, because some relatively cheap foods are not as poor in quality as you might have been led to believe.

Natural Foods

Natural pet food: a review of natural diets and their impact on canine and feline physiology (2014) Buff PR, Carter RA, Bauer JE & Kersey JH Journal of Animal Science 92(9) pp3781-3791 says "The term "natural," when used to market commercial pet foods or pet food ingredients in the United States, has been defined by the Association of American Feed Control Officials and requires, at minimum, that the pet food be preserved with natural preservatives. However, pet owners may consider natural as something different than the regulatory definition."

The Association of American Feed Controls Officials (AAFCO) has also stated "in an effort to appeal to customers, marketers have increasingly used the term on pet food product labeling", and says "Natural is a liberal term that includes more ingredients than it excludes—most pet food ingredients are derived from “plant, animal or mined sources." A feed ingredient can be subject to a number of commonly-used processes during the manufacturing process and still be deemed natural."

Human Grade Foods

Some people tell me they have always fed human grade foods and are concerned that therapeutic kidney diets are not of this quality. Can we eat it? (2009) Lau E Veterinary Information Network quotes the chair of the Association of American Feed Control Officials’ Pet Food Committee as saying that human grade food "is essentially a made-up term used by marketing interests to describe and promote products in light of anthropomorphic responses people have to their pets.”

AAFCO says "There have been “human-grade” claims on some pet foods for a few years. This term has no definition in any animal feed regulations. Extremely few pet food products could be considered officially human edible or human-grade. A pet food that actually met these standards would be expensive. While pet owners can buy what they feel is best for their pet, they should understand the definitions and the odds."

Please also read the section above about high quality protein from a CKD perspective.

Many people are reluctant to feed by-products, fearing they are not good quality ingredients. AAFCO defines meat by-products as "the non-rendered, clean parts, other than meat, derived from slaughtered mammals. It includes, but is not limited to, lungs, spleen, kidneys, brain, livers, blood, bone, partially de-fatted low temperature fatty tissue, and stomachs and intestines freed of their contents. It does not include hair, horns, teeth and hoofs. It shall be suitable for use in animal feed. If it bears a name descriptive of its kind, it must correspond thereto.”

Food Data Tables

It is not a case of looking at the tables and simply buying the food nearest the top of the table that is available to you locally. I am not recommending any of these foods. The tables simply list commercial cat foods in order of phosphorus content. I am not recommending any of these foods.  

Many senior foods are relatively low in phosphorus and protein, but they may also be lower in fat, which is not ideal for cats who are already on the thin side, or for older cats who tend to have poor fat digestibility.

Fancy Feast in the USA (the nearest UK equivalent is Purina Gourmet Gold) is often a big hit with cats but sadly it now has much higher phosphorus levels than it used to, so would not be my first choice, though it is worth keeping it in stock for times of crisis.

Personally I would not feed fish-based foods exclusively. See below for more on this.

The Food Data Tables: How to Use page has more information about how to use the tables.

See Persuading Your Cat to Eat for more information on CKD-friendly treats.

Foods for Cats with Other Conditions (Diabetes, Food Allergies or IBD, FLUTD)

Diabetes

For information on diet for cats with both diabetes and CKD, please see the Diabetes page.

Food Allergies or IBD (Inflammatory Bowel Disease)

Royal Canin has a dry food in the USA called Feline multifunction renal support with hydrolyzed protein which is designed for cats with both CKD and food allergies. It has a phosphorus level of 0.70% and a protein level of 29.35%.

Trovet, a Dutch company, produces Renal Venison RID food in both canned and dry versions for those in the UK or Europe, with phosphorus levels in the 0.50-0.65% range . Some of the Integra Protect Renal foods are grain-free.

BalanceIT has a video about the nutritional requirements of cats with food allergies.

Foods for Cats with Struvite Crystals (Feline Lower Urinary Tract Disease)

These foods are acidified and are therefore not suitable for most CKD cats (see below).

If your cat has calcium oxalate crystals or stones, most therapeutic kidney diets are suitable for this problem, see Kidney Stones.

Some people feed their cat a homemade diet, either raw or cooked. Since cats have very complex nutritional needs, this is not something which should be undertaken lightly; you need to do a lot of research in order to ensure that you are providing correct levels of essential nutrients. Pet Diets says "Unless properly formulated by a nutritionist, diets made at home are not likely to be nutritionally complete and balanced. The nutritional profile of any diet—including homemade diets—depends on how the recipe was formulated, the nutrient content of the ingredients, and how the owner prepares the diet."

Evaluation of recipes for home-prepared diets for dogs and cats with chronic kidney disease (2012) Larsen JA, Parks EM, Heinze CR & Fascetti AJ Journal of the American Veterinary Medical Association 240(5) pp532-8 found that many of the recipes analysed in the study would not meet nutritional needs. It is particularly important to get the ratio of phosphorus to calcium correct, and to ensure that you are providing enough taurine — taurine deficiency can cause blindness and heart failure. You also need to be particularly careful with raw diets since these may increase the risk of salmonella poisoning.

Evaluation of the nutritional adequacy of recipes for home-prepared maintenance diets for cats (2019) Wilson SA, Villaverde C, Fascetti AJ & Larsen JA Journal of the American Veterinary Medical Association 254 pp1172-1179 analysed 114 recipes for homemade food (some of which were provided by vets) from books (66 foods) and online (48 foods) and compared them with the guidelines issued by Your cat's nutritional needs (2006) National Research Council. There was not enough information to properly analyse ten of the recipes. None of the remaining recipes met all the NRC guidelines. Eight of them contained potentially toxic ingredients such as onion or garlic. More than 50% of the recipes did not contain enough taurine. and lacked other vital nutrients or exceeded the safe limit for others. The study concludes "Problems with nutritional adequacy were identified in all evaluated HPMD [home-produced maintenance diet] recipes. Appropriate formulation of HPMDs requires specialized knowledge of nutrition and use of computer software to avoid potentially harmful nutrient deficiencies."

Home Prepared Dog and Cat Diets (2010) Schenck P has recipes from a vet. Scroll down to Cat Recipe Nutritional Breakdowns Renal, and click on http next to Cat Recipe Nutritional Breakdowns Renal. An excel file will download with five different recipes for CKD cats. Some people have expressed concern regarding baking soda and calcium carbonate being interchangeable in the recipes. Dr Schenck actually addresses this issue on her Amazon page. Please note the comment about working with your vet.

Pet Place offers another recipe from the Pocket Companion to Small Animal Clinical Nutrition, 4th Edition.

BalanceIT is a site run by veterinary nutritionists. It sells supplements which are designed to be used in the free recipes which the site generates based on your cat's particular nutritional needs,  including one for kidney disease, but it also offers free recipes based on supplements (such as fish oils) available from health food stores. The site provides a nutritional breakdown of the recipe you create on a metabolisable energy basis.

Pet Diets in the USA has veterinary nutritionists who  can design a personalised diet for your cat if required.

University of California at Davis in the USA can devise a diet to suit your cat if your vet contacts them and provides current bloodwork. The personalised diet cost around US$250 in 2015.

The American College of Veterinary Nutritionists can help you find a veterinary nutritionist in the USA.

USDA FoodData Central is a database where you can search for any food ingredient and get a nutritional breakdown, including phosphorus and protein levels.

Pet Place provides a recipe for Hill's homemade CKD food. This recipe was apparently originally provided by Hill's to vets to offer to people whose cats would not eat a commercial diet. Other versions of this recipe which I have seen also included two cups of rice.

Felini Renal Supplement is a supplement for homemade diets available from Zooplus which is apparently phosphorus-free. I have no idea if it is the correct balance, so please check before using.

Your cat's nutritional needs (2006) National Research Council report that "If given free access to food, cats will eat between 12 and 20 meals a day, evenly spread out over the 24-hour light-dark cycle. It goes against the nature of the cat to force it to eat only one meal a day."

Effects of feeding frequency on water intake in cats (2005) Kirschvink N, Lhoest E, Leemans J. Delvaux F, Istasse L, Gustin P, Diez M Journal of Veterinary Internal Medicine 19 p476 found that cats fed more frequently increased their fluid intake. Free feeding a CKD cat has an additional benefit, namely that feeding little and often may reduce the problem of excess stomach acid, a common problem in CKD cats.

Petco sells a number of different feeders.

Amazon sells the Catmate. It also sells  another mode.

Amazon sells the Petsafe five meal feeder.

Pet Planet sells the Catmate two meal feeder.

Zooplus sells the Trixie timed feeder.

Dry Food versus Canned Food

Most dry cat foods only contain 8-10% moisture, so cats who eat dry food do tend to drink more than cats fed on wet food, but they simply cannot take in as much moisture overall as a cat fed on wet food. The carnivore connection to nutrition in cats (2002) Zoran D Journal of the American Veterinary Medical Association 221 pp1559-67, states "cats eating commercial dry foods will consume approximately half the amount of water (in their diet and through drinking), compared with cats eating canned foods...In older cats that tend to produce urine with a lower concentration, an increase in water consumption becomes even more important to avoid dehydration and development of prerenal azotaemia."

This does not mean that dry foods cause CKD. Apparent total tract energy and macronutrient digestibility and fecal fermentative end-product concentrations of domestic cats fed extruded, raw beef-based, and cooked beef-based diets (2012) Kerr KR, Vester Boler BM, Morris CL, Liu KJ, Swanson KS Journal of Animal Science 90(2) pp515-22 found that there was no difference in urine concentration between cats fed the three types of diet used in the study (dry food, raw food and home-cooked food). In fact, the cats fed the raw and homemade diets had higher creatinine levels than the cats fed the dry food, though still within range (these were healthy cats). A later study, Risk and protective factors for cats with naturally occurring chronic kidney disease (2017) Piyarungsri K & Pusoonthornthum R Journal of Feline Medicine & Surgery 19(4) pp358-363 found that feeding dry cat food might actually be "a potential protective factor against CKD in cats."

Transitioning your cat from dry food to wet food Johnson-Bennett P has tips on switching your cat from dry to canned food.

One study, Epidemiologic study of relationships between consumption of commercial canned food and risk of hyperthyroidism in cats (2004) Edinboro CH, Scott-Moncrieff JC, Janovitz E, Thacker HL & Glickman LT Journal of the American Veterinary Medical Association 224 (6) pp 879-886, indicates that cats who eat canned food, particularly from pull-ring cans, appear to be at increased risk of developing hyperthyroidism. It is thought that this may be related to the lining used in these cans, bisphenol-A (BPA), a potential endocrine disrupter. It is therefore probably worth trying to feed your cat food from foil pouches or plastic trays rather than from cans. If you do use cans, be sure to store any leftover food in glass containers in the fridge rather than in the tins themselves. The University of Warwick has more information on this.

Effect of water content in a canned food in voluntary food intake and body weight in cats (2011) Wei A, Fascetti AJ, Villaverde C, Wong RK & Ramsey JJ American Journal of Veterinary Research 72(7) pp918-23 found that healthy cats fed a canned diet ate more than cats fed the same diet in freeze-dried form, but took in less energy and "had a significant decrease in body weight." This is perhaps because the amount of water in canned foods makes the cat feel full more quickly.

Dry foods and risk of disease in cats (2008) Buffington CAB Canadian Veterinary Journal 49 p561-3 states that there is little evidence that dry food contributes to diabetes or ill health generally in cats.

AAFP-AAHA Feline Life Stage Guidelines (2010) state (page 48) "Both canned and dry food have been found to support health during all life stages. The panel examined published peer-reviewed evidence-based studies in healthy, client-owned cats for any significant health effect of: feeding canned versus dry food (including contribution to dental health); providing a variety of foods versus a consistent diet; feeding high protein, low carbohydrate versus lower calorie and high fiber diets; feeding raw diets; providing dietary supplements, or access to grass or plants.  Based on the available data, specific recommendations in favor of any of these practices cannot be made."

PetCoach has information on both onion and garlic.

ASPCA has detailed information on onion and also mentions garlic.

Allium species poisoning in dogs and cats (2011) Salgado BS, Monteiro LN & Rocha NS Journal of Venomous Animals and Toxins including Tropical Diseases 17(1) pp4-11 found that all allium species can be toxic to cats and dogs but that cats are 2-3 more times susceptible to damage than other species. It states that poisoning can occur if a 10lb cat eats 10oz (250g) of onion and that it can still be dangerous even if the cat eats smaller amounts over several days.

How much onion or garlic is toxic to pets? (2012) Gwaltney-Brant S is an article by a veterinary toxicologist.

Allium species poisoning in dogs and cats (2005) Cope RB Veterinary Medicine 100 (8) pp562-566 mentions that onions, garlic, leeks and chives are potentially toxic to dogs and cats, and that problems may occur after consumption of a single large quantity or repeated consumption of small amounts, even of dietary supplements rather than garlic or onion themselves.

Your cat's nutritional needs (2006) National Research Council in the USA provides a summary of the findings from the Committee on Examining the Safety of Dietary Supplements for Horses, Dogs and Cats (2008) and states that the committee was unable to determine a presumed safe intake level of garlic for cats.

Pet Diets is a site owned by Dr Rebecca Remillard, a veterinary nutritionist, which states "the possibility of developing a Heinz body hemolytic anemia appears to be variable between pets, and it is not possible to predict which animals may or may not have such a reaction to onion or garlic." Search for garlic, and it is in the answer to the last question on page 3 (Is it OK to give my pet a garlic pill once a week?)

Onions a little known threat (2002) Yin S San Francisco Chronicle has an article by a vet which mentions both onion and garlic.

Heinz body anemia in cats(2002) Tarigo-Martinie J & Krimer P University of Georgia College of Veterinary Medicine discusses Heinz body anaemia.

Haematologic changes associated with the appearance of eccentrocytes after intragastric administration of garlic abstract to dogs (2000) Lee KW, Yamato O, Tajima M, Kuraoka M, Omae S & Maede Y American Journal of Veterinary Research 61(11) pp1446-50 found that HCT levels reduced in dogs fed garlic extract, and Heinz bodies were detected. The conclusion was that "foods containing garlic should not be fed to dogs." Cats are even more sensitive to Heinz body anaemia than dogs, so this advice applies even more so to cats.

This type of food is acidified because it is designed to treat a different kind of problem called FLUTD (Feline Lower Urinary Tract Disease), where the cat's urine is too alkaline (sometimes referred to as struvite crystals). These foods are not intended for CKD cats at all, because CKD cats tend to have quite high acid levels anyway. Acidified foods may also have the effect of increasing the amounts of potassium lost in the urine, which is bad for most CKD cats.

You should also avoid foods that contain cranberries or additional vitamin C for similar reasons.

If your cat has both CKD and struvite crystals, click here.

Firstly, it can be hard to create a proper balanced diet. It's not just a case of plonking a piece of raw chicken on a plate and thinking you've cracked it. You need the correct balance of nutrients, and it isn't easy. Please see homemade foods for more information.

Secondly, it can be hard to know the protein and phosphorus content of the food you are feeding.  The USDA National Nutrient Database may help with this — it is a database where you can search for any food ingredient and get a nutritional breakdown, including phosphorus and protein levels.

The main concern for CKD cats is the risk of infection, because CKD cats are immune-compromised, so are more at risk of infection. Septicemic salmonellosis in two cats fed a raw-meat diet (2003) Stiver SL, Frazier KS, Mauel MJ &Styer EL Journal of the American Animal Hospital Association 39 pp538-542, found that raw foods may carry a greater risk of salmonella poisoning. Salmonella bacteriuria in a cat fed a salmonella-contaminated diet (2015) Fauth E, Freeman LM, Cornjeo L, Markovich JE, Janecko N & Weese JS Journal of the American Veterinary Association 247(5) pp525-530 reports on a cat fed a commercial diet that was not processed in the same way as most cat foods. It concludes "Such contamination is of particular concern with raw meat-based diets or diets that have not undergone standard industry cooking practices."

Highly suspected cases of salmonellosis in two cats fed with a commercial raw meat-based diet: health risks to animals and zoonotic implications (2017) Giacometti F, Magarotto J, Serraino A & Piva S BMC Veterinary Research 13(1) p224 reports on two cats from the same household suspected of having salmonella (which was found in their faeces) after being fed a homemade raw diet. It concludes "RMBD should be fed to pets with caution as they could lead to infection, especially in animals with impaired host immune defences."

Evaluation of two raw diets vs a commercial cooked diet on feline growth (2017) Hamper BA, Bartges JW & Kirk CA Journal of Feline Medicine and Surgery 19(4) pp424-434 compared the feeding of two raw foods and commercial canned food to healthy kittens. It found that all of the diets supported feline growth, but that "Salmonella serovar Heidelberg and C difficile enterotoxin were detected in the feces of some of the raw feeders, substantiating pathogen exposure and risks to both animal and owner."

Survival of Salmonella Copenhagen in food bowls following contamination with experimentally inoculated raw meat: effects of time, cleaning and disinfection (2006) Weese JS & Rousseau J Canadian Veterinary Journal 47(9) pp887–889 found that salmonella could persist in bowls used to hold raw meat despite thorough cleaning. The study states that this was surprising, "particularly their survival following soaking in bleach and washing in a dishwasher at 85°C. Bleach is typically a highly effective disinfectant that would be expected to kill Salmonella spp. However, bleach is less effective in the presence of organic debris, so possibly the small amount of food residue in the bowl was enough to permit survival of the Salmonella sp. in some cases. This likely accounts for the finding that only scrubbing followed by soaking in bleach was effective at reducing the Salmonella sp. contamination. However, even this method of disinfection did not completely eliminate Salmonella bacteria in all bowls."

Salmonella is not the only risk: Raw meat diets spark concern (2005) is a report by the Journal of the American Veterinary Medical Association which found that 99% of raw meat samples intended for dogs were contaminated with a variety of bacteria. Some people believe that freezing the food before feeding kills pathogens but the New Zealand Food Safety Authority explains that this is not necessarily the case.

Tuberculosis due to Mycobacterium bovis in pet cats associated with feeding a commercial raw food diet (2019) O’Halloran C, Ioannidi O, Reed N, Murtagh K, Dettemering E, Van Poucke S, Gale J, Vickers J, Burr P, Gascoyne-Binzi D, Howe R, Dobromylskyj M, Mitchell J, Hope J & Gunn-Moore D Journal of Feline Medicine and Surgery 21(8) pp667-681 reports on an outbreak of TB in cats in the UK. Five of the six cats showing symptoms died, and another seven cats living in the same households were also found to have TB. In one case, the cat's caregiver also had to be treated for TB. All of the cats were fed Natural Instinct wild venison food and the study states "the only probable source of infection is that the cats were all exposed to M bovis via the same commercially available raw food."

Current knowledge about the risks and benefits of raw meat-based diets for dogs and cats (2013) Freeman LM, Chandler ML, Hamper BA & Weeth LP Journal of the American Veterinary Medical Association 243(11) pp1549-1558 discusses the pros and cons of raw meat-based diets, and mentions that a study of dogs found that dogs fed a raw diet had significantly higher BUN, creatinine and HCT levels than dogs not fed such a diet.

Evaluating phosphorus, calcium and magnesium content in commercial cat foods (2020) Summers SC, Stockman J, Larsen JA, Zhang L & Rodriguez AS Journal of Veterinary Internal Medicine 34(1) pp 266-273 states "Of the 82 study foods, 7 foods (9%) contained concentrations of total P [phosphorus] (≥4.8 g/1000 kcal) that previously were demonstrated to cause a rapid decline in renal health in adult cats when most of the P was provided by inorganic P sources. Of these 7 foods with total P ≥4.8 g/1000 kcal ME, most (4/7; 57%) were raw foods, which is possibly attributable to these foods being high in protein and possibly bone derivatives, the main source of organic P in pet food."

Although I often hear people extolling the apparent benefits or raw, there is no research that I am aware of into the superiority or otherwise of raw diets for cats, and certainly not for CKD cats. In Advising clients who feed raw diets to pets (2005) NAVC Clinician's Brief, Dr R Remillard, a veterinary nutritionist, says "No scientific evidence exists that a raw diet is superior to any dry or canned pet food. As a result, this practice is associated with health risks to pet and family with no demonstrable benefit." Ten years later, nothing had changed. Pet food myth busters: answering common questions owners ask about pet food (2015) LM Freeman NAVC/WVC Symposia Proceedings says "Despite anecdotal reports from pet owners and even some veterinarians, there is currently no evidence that raw foods offer any benefits over cooked ones. There is substantial evidence, however, that raw foods may be associated with nutritional deficiencies, bacterial and parasitic infections, and other health concerns in pets. These foods also pose potential risk to people-especially those that are immuno-compromised, such as young children, the elderly, and patients receiving immune-modifying drugs or who have cancer."

The American Veterinary Medical Association advises against feeding raw. If you already feed a raw diet which your cat enjoys and with which you have had no problems, please do discuss whether to continue with your vet. If you have not previously fed raw, I would not recommend starting it because of the possible risks of infection and because it can be quite a change for an already sick cat. There are a few commercially available raw foods which are pasteurised.

Tufts University College of Veterinary Medicine discusses raw diets.

PetMD has an overview of steatitis.

Pet Place has some information about this condition.

Armed Forces Institute of Pathology discusses a case of steatitis in a cat (click on Case Study III) - this cat was put to sleep.

Lack of Taurine

Fish lacks taurine, an amino acid which cats need to obtain from their food. A lack of taurine in a cat's diet can cause heart and eye problems.

Pro Vet states that "like meat, it is deficient in calcium with an inverse calcium:phosphorus ratio. Coley (or Saithe) a popular fish with cat owners in the UK and the fillet cut contains 15-20 mg calcium per 100g but over 200 mg phosphorus per 100g, a Ca:P ratio of 1:10. Cod and other white fish are similar."

One study, Evaluation of dietary and environmental risk factors for hyperthyroidism in cats (2000) Martin KM, Rossing MA, Ryland LM, DiGiacomo RF, Freitag WA Journal of the American Veterinary Medical Association 217(6) pp853-856, found that "cats that preferred fish or liver and giblets flavors of canned cat food had an increased risk" of developing hyperthyroidism. This may be because of the iodine content in the food.

The US Food & Drug Administration advises pregnant women not to eat tuna. The US Environmental Working Group, which worked on the studies with the FDA, believes that human-grade tuna has unusually high levels of the toxic metal methylmercury. It recommends that pregnant women should not eat tuna at all, and that children should eat tuna no more often than once a week. Human-grade tuna tends to consist of the white "meat", while animal-grade tuna tends to consist of the lower grade red "meat", so, at least in theory, animal-grade tuna could contain more pollutants.

A 2003 study in The Lancet indicated that eating tuna may not be a problem for pregnant women and children after all (Web MD has a report on this), but I think it might be wiser to err on the side of caution with a sick CKD cat.  A tuna fish diet influences cat behavior (1988) Houpt KA, Essick LA, Shaw EB, Alo DK, Gilmartin JE, Gutenmann WH, Littman CB, Lisk DJ Journal of Toxicolology & Environmental Health 24(2) pp161-72 found that "Cats fed the tuna had elevated tissue levels of mercury and selenium."

What is in commercial cat and dog food? The case for mercury and ingredient testing (2019) Dunham-Cheatham SM , Klingler K, Peacock M , Teglas MB & Gustin MS The Science of the Total Environment 684 pp276-280 found mercury in 16 of the first 100 cat food samples they examined. Most of these foods were tuna, as you might expect, but mercury was also found in some foods containing other types of fish.

Thiamine (Vitamin B1) Deficiency

As you can see, feeding fish regularly has some serious health implications for cats. A little fish occasionally is unlikely to be cause for concern, and feeding it for a few days during a time of crisis should not be a problem (in fact, if you're in the UK, I find feeding a bit of fish from the chippy - batter removed - can help with poor appetite in many cats), but I would not recommend feeding it for any length of time or too often, especially tuna.

Please also read the section immediately above about fish and tuna.

Most commercial cat foods based on fish are usually complete because they do not only contain fish, and are formulated with additional ingredients such as taurine and Vitamin E to prevent steatitis and taurine deficiency. However, you do need to check the can closely because some commercial fish-based foods are not complete foods e.g. some Applaws foods in the UK.

One possible compromise is to add the water in which tuna is packed to your cat's veterinary or other diet in order to make it more palatable. See tuna water for more information.

Cat Food Recalls

Cat food recalls are frighteningly common. In 2007 quite a few cats either died or suffered permanent kidney injury because of cat food contamination (see 2007 Cat Food Recall).

In the UK in 2021 there were a number of cases of pancytopenia, a serious condition which damages blood cells. A number of brands, including Sainsburys and Applaws, have had some of their foods recalled, although a causative link has not yet been established. The Food Standards Agency has a list of recalled foods. The Royal Veterinary College has an update dated August 2021 stating that they have treated 563 cats, of whom 63% have died.

Petful has up to date information on cat food recalls in both the USA and UK.