Don't Feed These to a Cat with Kidney Disease!

Although there is no cure for CKD, tailored nutrition can drastically support cats by controlling and supplementing certain nutrients to promote renal health. In this article, we'll share the foods to avoid if your cat suffers from CKD.
a gray and white cat sitting next to an orange bowl

Chronic kidney disease (CKD) is a long-lasting health issue that is estimated to affect around 30-40% of cats over the age of 10. Although there is no cure for CKD, tailored nutrition can drastically support cats by controlling and supplementing certain nutrients to promote renal health. In this article, we'll share the foods to avoid if your cat suffers from CKD.

What is Chronic Kidney Disease?

a cat is being checked by vet for chronic kidney disease

The kidneys of your cat have thousands of tiny filters called nephrons. These filters work together to remove harmful toxins from the bloodstream while recycling essential substances like amino acids and minerals. Chronic Kidney Disease (CKD) occurs when a nephron function is lost due to a disease, an injury, or an inherited condition. When there is insufficient nephron function, significant substances are lost while toxins and waste products that are typically eliminated begin to accumulate in the bloodstream. This accumulation can damage the kidney tissue, cause clinical signs, and create progressive kidney injury.

How Can I Spot the Signs of Kidney Disease?

Kidney disease can be challenging to detect in cats since it may not show any visible signs until a considerable level of kidney function is already lost. However, some common symptoms include weight loss, increased thirst, and frequent urination.

The early signs of Chronic Kidney Disease (CKD) are subtle and can be easily missed. Therefore, it is highly recommended that your pet have regular check-ups with a veterinarian.

Does Dry Kibble Cause Kidney Failure In Cats?

a black and white cat sitting next to a bowl of food

Your cat may prefer one type of food over another. Some cats prefer wet food from a pouch, while others prefer dry kibble. You may also have come across conflicting advice in pet publications or from other cat owners about the impact of dry food on your cat's health, such as its effect on kidney health, teeth, or urinary tract. However, it is essential to note that the nutritional content is more important than whether the food is dry or wet.

Ingredients In Your Cat's Food

Cats are carnivores, meaning they need fatty acids and meaty proteins. Their diet must be high in animal proteins and fats and low in carbohydrates. While it is acceptable for dry kibble to contain a small amount of carbohydrates, checking the labels for vegetable or grain products is essential. Too many carbohydrates in a cat's diet increase the risk of developing certain health problems, like obesity and diabetes. Although cats require some carbohydrates, an excessive amount can harm their health.

Many dry cat foods contain rice, cornmeal, and grains to help cats process the kibble, which can result in more carbohydrates in their food intake. On the other hand, wet cat food contains fewer carbohydrates. Some cat foods may even contain vegetable proteins instead of meat, which is not ideal for cats who love to eat meat.

When you shop for food, read the ingredient list on your cat's food and avoid items containing peas, beans, corn, potatoes, or rice. You should also know the nutrients in your pet's food and ensure they meet your cat's dietary requirements.

Can Dehydration Cause Cat Kidney Failure?

a black and white cat drinking water from a faucet

Cats typically don't drink much water during the day due to their low thirst drive compared to other animals. Even if they are dehydrated, they may not feel thirsty. So, cats mostly get water from their food.

Because of its water content, wet food is better than dry food. It's also more similar to the food cats eat in the wild. Extra moisture in their diet can promote better cat bladder and kidney health. If cats remain dehydrated for a long time, it can irritate their urinary tract and potentially lead to kidney disease.

If your cat prefers dry food, try sprinkling some water on it. This way, your cat can benefit from wet food without switching its meals entirely. However, it's always advisable to consult your vet for specific advice tailored to your cat's needs.

Foods To Avoid

two cats sitting next to each other in metal bowls

The following foods are not recommended for cats with CKD:

onion and garlic

  • Foods marketed for urinary tract health
  • Raw food diets
  • Fish (especially tuna)

Let us discuss them one by one.

Onion and Garlic

Never feed cats anything containing onions. Onions contain an alkaloid disulfide compound that can damage red blood cells and cause severe anemia called Heinz body anemia in cats. Even a tiny amount of onion can be fatal to particularly susceptible cats, and symptoms may take several days to appear.

Garlic is a member of the same family, and some believe the same caution applies to garlic. The Veterinary Poisons Information Service (VPIS) in the UK dealt with sixteen cases of allium poisoning in cats, including garlic. Allium species, including onions, garlic, leeks, and chives, are potentially toxic to dogs and cats, and cats are 2-3 times more susceptible to damage than other species. Poisoning can occur if a 10lb cat eats 10oz (250g) of onion, and even smaller amounts over several days can be dangerous.

Foods for Urinary Tract Health

It is a common misconception that foods marketed as "supporting urinary tract health" or "magnesium-controlled" are suitable for cats with chronic kidney disease (CKD). However, this is not true. These foods treat Feline Lower Urinary Tract Disease (FLUTD), where the cat's urine is too alkaline and may contain struvite crystals. These foods are acidified to treat FLUTD, which can adversely affect CKD cats since they already tend to have high acid levels. Furthermore, acidified foods can increase potassium loss in the urine, which harms most CKD cats. Therefore, it is recommended that you avoid foods containing cranberries or additional vitamin C for similar reasons.

Raw Diet

Some people think feeding their cats a raw diet will solve all their problems associated with chronic kidney disease (CKD). However, it is not as simple as that. While raw diets are not necessarily bad, they are not a magic cure for CKD. There are some possible problems associated with feeding a raw food diet to cats with CKD:

Firstly, creating a balanced diet can be challenging. It is not just a matter of putting a piece of raw chicken breast on their dish and thinking that you have provided your cat with everything they need. You must ensure that your cat receives the correct balance of nutrients, which can be challenging.

Secondly, it can be hard to determine the protein and phosphorus content of the raw food you are feeding. One helpful resource is the USDA National Nutrient Database, which provides a nutritional breakdown of various food ingredients, including their phosphorus and protein levels.

One of the main concerns for cats with CKD is the risk of infection. These cats have a weakened immune system, which puts them at greater risk of infection. Some studies have suggested that raw foods may carry a higher risk of salmonella poisoning. For instance, two cats fed a raw-meat diet were found to have septicemic salmonellosis in 2003.

Another concern is that raw meat-based diets may lead to contamination, which poses a risk to both the cat and its owner. For instance, in 2017, two cats from the same household were suspected of having salmonella after being fed a raw homemade diet. The study concluded that raw meat-based diets should be cautiously fed to pets, especially animals with already impaired immune defenses.

A 2017 study found that some raw foods may contain Salmonella serovar Heidelberg and C difficile enterotoxin, which can harm cats and their owners. Despite thorough cleaning, Salmonella bacteria can persist in raw meat bowls.

While the incidence of salmonella in cats is generally low, cats with CKD have a higher risk of contracting the disease, which could be life-threatening. Furthermore, raw meat diets are contaminated with various bacteria, and in a 2005 study, 99% of raw meat samples intended for dogs were found to be infected.

Lastly, a 2019 study reported an outbreak of tuberculosis in cats in the UK associated with feeding a commercial raw food diet. Five of the six cats showing symptoms died, and another seven cats living in the same households were also found to have TB. The study states that all the cats were fed a particular brand of wild venison food, which was the likely source of the infection.

In summary, feeding a raw food diet to cats with CKD poses some risks. While raw diets are not necessarily bad, cat owners need to be aware of the potential dangers and be cautious to minimize the risk of infection.

Fish, Particularly Tuna

a bengal cat sitting next to a can of food

There are several reasons why fish is not an ideal food for cats. We'll break them down:


Feeding a cat a diet solely of fish can lead to stomatitis or yellow fat disease. A vitamin E deficiency from an unbalanced diet causes this.

Initially, the cat may become nervous and eventually hypersensitive to touch due to nerve-ending inflammation throughout its skin. The best course of treatment is to administer significant doses of vitamin E under the supervision of a veterinarian and to cease feeding the cat any food containing vegetable or mineral oil, which could cause further decreased levels of vitamin E. PetMD provides an overview of statistics. Sadly, the cat in the case study was put to sleep.

Lack of Taurine

Fish lack taurine, an amino acid that cats require from their food. The absence of taurine in a cat's diet can lead to heart and eyesight issues.

Poor Calcium to Phosphorus Ratio

Many types of fish that are popular among cat owners lack calcium and have an inverse calcium-to-phosphorus ratio. A cod fillet cut typically contains 15-20mg of calcium per 100g but over 200mg of phosphorus per 100g. This results in a calcium-to-phosphorus ratio 1:10, which is not ideal for cats. Other white fish have similar nutritional profiles.


According to a study, cats that prefer fish—or liver and giblets-flavored canned foods are at an increased risk of developing hyperthyroidism. This is possibly due to the high iodine content in these food types.

Additional Risks for Tuna

  • Addictive Behavior: Some cats can become addicted to tuna, but it's not a balanced diet, leading to health problems.
  • Neurologic Disturbances: There have been reports of neurological issues in cats fed a tuna-only diet for 7-11 months despite the balanced nature of commercial tuna-based cat foods.
  • Mercury Toxicity: Consuming commercial fish products such as tuna may lead to chronic poisoning in humans and animals, including cats. The US Food & Drug Administration advises that pregnant women should not eat tuna due to its high levels of the toxic metal methylmercury. Similarly, the US Environmental Working Group recommends that pregnant women avoid eating tuna altogether, while children should consume it no more than once a week. While animal-grade tuna tends to consist of lower-grade red "meat" and may contain more pollutants, human-grade tuna is believed to have unusually high levels of methylmercury.
    While a 2003 study in The Lancet suggested that eating tuna may not harm pregnant women and children, given a sick CKD cat, it may be safer to err on the side of caution.
  • Thiamine (Vitamin B1) Deficiency: Feeding fish to cats regularly can have profound health implications. For instance, cats who eat tuna regularly can develop vitamin B1 (thiamine) deficiency, which can lead to neurological symptoms such as the inability to hold up the head, dilation of the pupils, loss of balance, seizures, and even death if left untreated. If you're considering feeding your catfish, it's worth checking out some resources that detail the dangers of feeding fish to cats.
    While occasional fish consumption is unlikely to cause any harm, it's best to avoid feeding it to cats regularly or for long periods, especially tuna. However, if necessary, feeding a little bit of fish for a few days may be fine.

Commercial Fish-Based Foods

I divide fish-based commercial foods for cats into two categories:

1. The "old school" type usually contains a mix of ingredients, such as chicken and tuna, and looks like typical cat food.

2. The newer type of food that contains only fish. These are often advertised as high quality and made with natural ingredients. They usually look like something you'd be served in a fancy restaurant. These types of food are becoming more popular, but they are generally manufactured in Thailand.

Most commercially available fish-based cat foods are complete meals containing additional ingredients like taurine and Vitamin E to prevent deficiency. However, you should check the label carefully because some commercial fish-based foods may not be complete.

The newer type of food that only contains fish is often shallow in both fat and calories, which means your cat may need to eat several cans a day or lose weight on such food. I wouldn't choose to feed my cat exclusively fish-based foods, and I wouldn't exclusively feed my cat tuna-based foods long-term.

However, most cats seem to enjoy the newer style of fish-based meals, so they may be helpful when your cat's appetite is poor. You can add a little to your cat's regular food to encourage them to eat. One possible compromise is to add the water in which tuna is packed to your cat's veterinary or other diet to make it more palatable.

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