Tanya's Comprehensive Guide to Feline Chronic Kidney Disease

These data are calculated on the basis of dry matter analysis. I know many people are very confused about why the data in the tables differ so much from the percentages shown on the cans or on manufacturers' websites.

I also know many people think they can just rush out and buy the first food on the list that their cat will eat but unfortunately it's not that simple.

Please read below to understand why the food data tables are calculated in this way and how best to use them.

Please read this page before contacting me to tell my data are incorrect — chances are you have misunderstood how I calculate the data. Yes, I know the information on the cans is not the same.

The Different Ways of Assessing Food Content

Unfortunately there are a number of different ways of assessing food content, which can make choosing a cat food a very confusing exercise. All these methods have their pros and cons.

Guaranteed analysis (GA): this is what most US manufacturers use.
Typical analysis: this is what most UK manufacturers use.
Metabolisable energy (ME): used by some manufacturers in many countries.
Dry matter analysis (DMA): this is what this website uses.

This page explains the differences between the different methods and why I use dry matter analysis.

Guaranteed Analysis - Used in the USA

Virtually all US cat food manufacturers provide their food data as Guaranteed Analysis (GA). This is to comply with AAFCO (Association of American Feed Control Officials) guidelines. AAFCO is responsible for overseeing pet food production in the USA, and its guidelines cover the production, labelling, and sale of pet foods. Guaranteed analysis is normally provided as As Fed data.

Unfortunately, guaranteed analysis is of only limited use when trying to compare foods for CKD cats. 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 "minimum values on food packages cannot be used to accurately estimate “as fed” amounts of Ca and P, and thus utilizing the label to identify foods low in P or Ca is not feasible."

This is because guaranteed analysis only provides maximum and minimum values, and the only ones which are compulsory are protein and fat (minimums), and fibre and moisture (maximums). If phosphorus is shown (and it is not compulsory), it is usually given as a minimum. This makes it very hard to assess whether a food is suitable for a CKD cat, for whom you need to know the exact amount or at the very least the maximum amount of phosphorus in particular. The minimum is potentially very misleading. For example, I could tell you "I have a minimum income of US$25,000" when in fact my income was US$250,000. I wouldn't have lied; on the other hand I wouldn't have given you meaningful information either.

Here's an example of how this affects foods. Let's say we are looking at a food with the following Guaranteed Analysis figures:

moisture: max 80%
phosphorus: min 0.20%

If we assume these values are correct, this gives us a dry matter analysis figure (see below) of 1% for phosphorus.

Now let's say the actual figures are:

moisture: 79%
phosphorus: 0.25%

This gives us a DMA figure of 1.19% for phosphorus, some 20% higher, so very different from the figures we came up with if we used Guaranteed Analysis figures.

Because of this, and because so many manufacturers are unable to provide information on a Dry Matter Analysis basis (in fact, a fair number don't even seem to realise there is a difference), there are quite a few foods missing from the food data tables I have created. Nevertheless, the tables contain over 1500 individual foods.

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 "A change in existing regulatory guidelines with regard to P maximums in foods formulated for cats should be considered in light of potential safety issues potentially impacting a subset of pet cats." But until this happens, I have to crunch numbers.

Decoding AAFCO Guidelines (2013) Larsen J Clinician's Brief Feb 2013 pp9-11 explains more about AAFCO's guidelines.

Typical Analysis - Used in Europe

Virtually all European cat food manufacturers provide their food data as Typical Analysis. This is to comply with EU legislation. Regulation 183/2005/EC on Feed Hygiene covers the safety of all animal feed, including pet food, in Europe. The UK Food Standards Agency has more information about the legal requirements for pet food. In the UK, over 90% of pet food manufacturers are also members of the Pet Food Manufacturers Association, and comply with its guidelines.

Unfortunately, typical analysis is of only limited use when trying to compare foods for CKD cats. This is because, although it is more reliable than Guaranteed Analysis, it does not allow for the moisture content in the food.

Metabolisable Energy (ME)

Metabolisable energy (ME) is another way of calculating the values in pet foods.

ME is the amount of energy available from a food for your cat to use once your cat has digested the food. It focuses on protein, fat and carbohydrate.

Since phosphorus is the most important value for CKD cats, I do not look at ME values, but they may be of some use for people with diabetic cats, who often look to feed foods with an ME value for carbohydrates of 10-12% or lower.

Dry Matter Analysis: Used on This Website

What we need ideally is dry matter analysis (DMA).

Cat foods vary in how much moisture they contain, which makes it difficult to compare them to each other. It is very hard, for example, to compare a canned cat food to a dry cat food because the former naturally contains much more water; and this affects all the percentages of the different nutrients.

Dry matter analysis is a way of comparing foods by assuming all the moisture content has been removed: this makes it easier to compare different products. Whenever this site mentions levels of the various components of foods, it is talking about them on the basis of dry matter analysis, which is not necessarily the same as what it says on the can.

Let's take an example. Let's say:

you give your cat a food with 80% moisture, a typical level for many canned foods;
the food apparently has phosphorus of 0.25%;
your cat eats 100g of the food.

It therefore appears that your cat is eating 0.25g of phosphorus (100g x 0.25%).

However, the food is 80% water. So of the 100g your cat has just eaten, 80g (80%) of it was simply water, and only 20% was actual food, or dry matter. So the amount of phosphorus is actually higher in percentage terms than it first appeared, i.e. your cat has eaten 0.25% divided by (100%-80%) or 1.25% phosphorus.

Another way of looking at it is to say that your cat food initially had 1.25% phosphorus. Then the manufacturer added 80% water. There is still the same total amount of phosphorus in the food, but at first the percentage appears lower because of the diluting effect of the water. So in order to understand exactly how much phosphorus your cat is eating, you need to discount the water in the food.

Dry Matter Analysis: Why My Figures Differ to Other Websites

I am sometimes asked why my data differ to those on other websites.

The values on some other sites provide figures on the basis of % caloric distribution for protein, fat and carbohydrate, and the number of mg of phosphorus in every 100 or 1000 calories of food.

There is nothing wrong with calculating figures in other ways, it is just a different way of looking at things. Websites designed for people with diabetic cats, for example, have a different nutritional focus.

My site gives the figures as a percentage of the food. In other words, whether you feed one ounce of food, or four ounces of food, my figures remain the same.

The main reason I use Dry Matter Analysis % is because that is the format which leading vets use when making recommendations for target nutrient intake in CKD cats.

Since I doubt you give food to your cat measured by calories, I would stick with my figures if you have a CKD cat.

Calculating Dry Matter Analysis Yourself

You shouldn't often need to calculate dry matter yourself because I've already done it for many foods. If you do want to do it yourself, you need to know the amount of moisture in the food and the amount of whatever you are measuring (often this will be phosphorus), and then you need to crunch the numbers a little.

Let's assume you have a food with a moisture content of 76% and a phosphorus content of 0.2% on an As Fed basis. This is the formula:

The dry matter in a food is always 100 - (% moisture in the food). So in this example, with 76% moisture, 100-76% leaves 24% dry matter.
You then have to divide the phosphorus content by the dry matter. In this case, you would divide 0.2% phosphorus by 24% dry matter, which gives 0.833% phosphorus content of this food on a Dry Matter Analysis basis.

Remember, using the data from cans of food in the USA for this exercise is often unreliable because the data on the cans tend to be maximums or minimums (they will be minimums for phosphorus)rather than actual data.

Scheyder Web Design has a DMA calculator.

PawDiet has a DMA calculator.

Catcentric has a DMA calculator.

The US Food and Drug Administration also explains about dry matter analysis (scroll down to Guaranteed Analysis).

What to Look For When Choosing a Food

Please don't just rush out and buy the first food at the top of the list! There are a number of issues to consider when choosing the best food for your cat's particular needs.

The tables simply provide information on the amount of the various components of the foods. This is only half the story. There is also the question of the quality of different cat foods, particularly what constitutes a high quality protein and which ingredients are the best. You can read more about these issues on the Which Foods to Feed and Nutritional Requirements pages.

If you want to check the actual ingredients in a food, either visit the brand's website (there is a list of US brands here) or visit a site such as Chewy which tells you the ingredients of the foods it sells. If you would like to discuss the various foods and ask what has worked for other people, join Tanya's CKD Support Group.

You also need to consider the calories in a food. Generally speaking, lower fat foods have fewer calories, as do gravy foods.

AAFCO Minimum Levels

US commercial adult foods certified as complete must meet the AAFCO guidelines for adult maintenance foods.

These are the minimum levels permitted by AAFCO (fibre is the only component which has a maximum level):

Dietary Component	Minimum Level for Adult Cats % on a DMA Basis
Phosphorus	0.50
Protein	26.00
Sodium	0.20
Fat	9.00

Phosphorus

If your cat's phosphorus level in blood tests is too high, this will make your cat feel ill and may make the CKD progress faster.

In order to reduce these risks, your goal is to have your cat's serum level of phosphorus (i.e. what your vet tests in bloodwork) no higher than 4.5 mg/dl (USA) or 1.5 mmol/L (international).

The easiest and most effective way to control blood phosphorus levels is by feeding foods low in phosphorus.

People sometimes think that if a food does not mention phosphorus on the label, it must not contain any. This is virtually impossible, especially if the food contains animal-based protein, as most cat foods do. As outlined in the table above, any American food labelled as an adult maintenance food must contain at least 0.5% phosphorus on a dry matter analysis basis and many foods contain far more than this.

Small Animal Clinical Nutrition — 6th Edition, Chapter 37, Chronic Kidney Disease (2019) Davenport D & Kirpensteijn J (Eds.) Mark Morris Institute states "To achieve beneficial effects, the recommended phosphorus levels for foods used to manage CKD are 0.3 to 0.6% DM for cats." DM means dry matter analysis (DMA), which is different to the percentage given on the can.
Ideally you want to feed a food with a phosphorus level under 0.5% according to Management of feline chronic renal failure (1998) Brown SA Waltham Focus 8 (3). No commercial adult food which meets AAFCO guidelines will meet this requirement because the minimum phosphorus level required by AAFCO is 0.5%.

Many of the manufacturers' websites show the phosphorus content of foods as g/1000 kcal. It is difficult to onvert this figure to the DMA equivalent, but as a guide, Building a strong recommendation for a veterinary therapeutic diet (2020) Roman G Vetted 115(1) reports on a conference at which Dr CR Heinze, a veterinary nutritionist at Cummings School of Veterinary Medicine at Tufts University, recommended diets for CKD cats with less than 2g/1000 kcal of phosphorus for Stages 1/2 and less than 1.25 g/1000 kcal for stages 3 and 4. The average standard commercial food, in contrast, will contain around 3 g/1000 kcal.

If your cat won't eat a therapeutic kidney diet, you still need your cat to eat. Since the minimum level of phosphorus in a non-therapeutic kidney food is 0.5%, you are not going to find a complete commercial food with phosphorus below this level, but you may be able to find a food in the table which has a low level of phosphorus which your cat will eat. The table lists foods in order of phosphorus content so you can clearly see which foods might be worth considering.

In order to keep your cat eating, you may have to have a less ambitious goal, at least to start with, of, say, feeding a food with less than 0.75% or less than 1% phosphorus.

But your ultimate goal should be to feed the lowest phosphorus food that your cat will eat.

Whichever food you opt for, always introduce a new food gradually (mix it with the food you've been using previously and gradually increase the percentage of the new food) so as to reduce the risk of tummy upsets.

If you are not feeding a therapeutic kidney food, you will probably have to give your cat a phosphorus binder. Please read the Phosphorus Binders page for more information.

Protein

The need for reduced protein for CKD cats is much debated, and may not be necessary for cats in the early stages of CKD. See Nutritional Requirements for more information.

However, since BUN levels are influenced by diet, it does often help the cat feel better if you restrict protein intake, particularly as the CKD progresses and BUN rises.

Most therapeutic kidney diets have protein levels of between 28 and 35% DMA.

When choosing a commercial food from the lists, I would not only look at the phosphorus level but also consider the protein level. That is to say, if for example I have two foods with the same phosphorus level to choose from and my cat will eat both of them, and one food has 32% protein while the other has 50% protein, I would normally choose the lower protein food.

Ohio State University College of Veterinary Medicine has stated that protein should never be reduced to less than 20% of calories. According to Small Animal Clinical Nutrition — 6th Edition, Chapter 37, Chronic Kidney Disease (2019) Davenport D & Kirpensteijn J (Eds.) Mark Morris Institute, this is around 24% on a dry matter analysis basis.

Personally I would try to feed a food with a protein level of 35% on a dry matter analysis basis, or as close to this as you can get.

Sodium

Since CKD cats are prone to high blood pressure, it is generally advisable to try to feed a food low in sodium.

Having said that, Effects of sodium chloride on selected parameters in cats (2006) Kirk CA, Jewell DE, Lowry SR Veterinary Therapeutics: Research in Applied Veterinary Medicine 7(4) pp333-346 found that there was actually no change in blood pressure in the CKD cats in this study, but levels of BUN, creatinine and phosphorus were higher in the cats eating a high sodium diet compared to those eating a low sodium diet.

The sodium content of therapeutic kidney diets varies widely. The minimum level permitted by AAFCO is 0.2%. It is unlikely that you need to go much higher than this.

As with protein, I would factor this into choosing a food. If for example I have two foods with the same phosphorus level and a similar protein level to choose from and my cat will eat both of them, and one food has 0.3% sodium while the other has 1% sodium, I would normally choose the lower sodium food.

Fat

As with protein, cats need relatively high levels of fat compared to a human or dog.

Fat does not result in a lot of waste products like protein, so processing it is not a strain on the kidneys. In fact, in most CKD prescription foods, the fat content is increased to compensate for the reduced protein levels.

Therefore a diet relatively high in fat can help an older cat to maintain his/her weight while placing less strain on the kidneys.

In other words, if you have a choice of two similar foods and you wish to maintain or even increase your cat's weight, it is probably better to choose the food with the higher fat content.

Sources of Data

I have spent hours contacting the various brands to obtain the correct information, and I have then crunched the numbers where necessary.

These analyses have been compiled in good faith from the information provided to me by the brands. I have obtained the data from their websites or in writing in order to avoid any misunderstandings. The data may not necessarily match the information on the cans, which show maximum values for moisture and phosphorus rather than actual values.

Unfortunately food formulations can change without warning, and therefore I cannot guarantee that the data are still accurate; no responsibility can be accepted. Several of the brands have asked me to emphasise that their non-therapeutic kidney diets are not intended for CKD cats.

For those juggling more than one health condition, the tables also includes some data for other therapeutic diets.

Although I don't recommend feeding raw foods to CKD cats, since I know some people may already be feeding them, data for these foods are included.

Please see the sidebar on the left or Cat Food Data Overview for links to the wet and dry food data tables, plus brand contact details and my opinion of their levels of helpfulness.

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This page last updated: 22 June 2025

Links on this page last checked: 22 June 2025

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TREATING YOUR CAT WITHOUT VETERINARY ADVICE CAN BE EXTREMELY DANGEROUS.

I have tried very hard to ensure that the information provided in this website is accurate, but I am NOT a vet, just an ordinary person who has lived through CKD with three cats. This website is for educational purposes only, and is not intended to be used to diagnose or treat any cat. Before trying any of the treatments described herein, you MUST consult a qualified veterinarian and obtain professional advice on the correct regimen for your cat and his or her particular requirements; and you should only use any treatments described here with the full knowledge and approval of your vet. No responsibility can be accepted.

If your cat appears to be in pain or distress, do not waste time on the internet, contact your vet immediately.

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If you wish to link to this site, please feel free to do so. Please make it clear that this is a link and not your own work. I would appreciate being informed of your link.