What to feed a cat with kidney disease

The best-supported food for a cat with chronic kidney disease is a prescription kidney diet chosen with your vet: restricted in phosphorus, moderate in high-quality protein, with added omega-3s, and ideally wet. In studies, cats with kidney disease fed these diets have tended to live longer and have fewer crises than cats kept on regular food.

There is one rule above that one. A cat that eats something beats a cat that refuses the perfect diet. Cats cannot safely go without food, so if your cat will not touch the kidney diet, the answer is a conversation with your vet, not a standoff at the bowl. For background on the disease, see our overview of kidney disease in senior cats.

What a kidney diet for cats changes

• Phosphorus is restricted. This is the change with the strongest evidence behind it.
• Protein is moderated and high quality. Enough to maintain muscle, with less waste for the kidneys to clear.
• Omega-3 fatty acids are added. Usually from fish oil.
• Potassium and B vitamins are topped up. Cats with kidney disease tend to lose both in their urine.
• Calories are concentrated. A cat with a small appetite gets more from each mouthful.
• Sodium is kept moderate, and the food is balanced to counter acid build-up in the blood.

Regular "senior" cat foods are not kidney diets. Our guide to choosing a senior cat food is for healthy older cats. After a kidney diagnosis, your vet picks the food based on the stage. Our guide to cat kidney disease stages explains what the stages mean.

Low protein cat food for kidney disease: moderated, not slashed

Cats are obligate carnivores. They need more protein than dogs or people, and older cats lose muscle easily. A diet with too little protein leaves a kidney cat thin and weak.

That is why kidney diets for cats reduce protein only moderately and use sources that are easy to digest. Phosphorus is the nutrient that matters most. In early disease, some vets hold off on a full kidney diet and focus on phosphorus and regular monitoring. Which approach fits your cat is your vet's decision.

Phosphorus and phosphate binders

Failing kidneys cannot clear phosphorus, so it builds up in the blood. High phosphorus makes cats feel ill and is linked with faster loss of the kidney function that remains.

The kidney diet is the first tool. If blood phosphorus stays above target, or your cat will only eat regular food, your vet may add a phosphate binder. It is a medicine mixed with meals that keeps some phosphorus from being absorbed. The type and the amount are set by your vet from bloodwork. Do not start one on your own.

Wet food, dry food and water

Wet food is usually preferred, because it brings water with it. Cats with kidney disease lose more water in their urine and dehydrate easily, and dehydration makes them feel worse and eat less.

Dry cat food for kidney disease does exist as a prescription diet, and it is a reasonable choice for a cat that will only eat dry. A dry kidney diet your cat eats is better than a wet one it ignores. To get more water in:

• Offer both wet and dry versions of the kidney diet, if your cat will take some of each.
• Put out several wide, shallow water bowls, away from the litter box.
• Try a water fountain. Some cats drink more from moving water.
• Ask your vet about stirring a little warm water into wet food.

If your cat still runs dry, your vet may prescribe fluids given under the skin, sometimes at home after they have shown you how.

How to switch a cat to a kidney diet

Slowly. Cats are suspicious of new food, and a sudden change often ends in refusal. Mix a small amount of the new food into the old, or set it out in a separate dish beside the usual food, and shift the balance over several weeks.

Start when your cat is feeling reasonably well. A food first met during nausea or a hospital stay can be refused for good. Do not hide pills in it. If one kidney diet fails, ask for another, because there are several prescription options in different flavors and textures.

Cat with kidney disease not eating

A cat that has eaten nothing for 24 hours needs a vet that day. Cats that stop eating can develop hepatic lipidosis, a serious liver condition, within days.

Poor appetite in kidney disease usually comes from nausea, mouth ulcers, dehydration or constipation, not pickiness. All of these are treatable. Your vet can prescribe anti-nausea medicine and appetite stimulants, including some made for cats that are applied to the skin of the ear, so no pill is needed. Never give human stomach remedies or painkillers. Acetaminophen, ibuprofen, naproxen and aspirin can kill cats.

At home, these tend to help:

• Warm wet food to lukewarm. It smells stronger. Stir it and check that it is not hot.
• Serve small, fresh portions often. Remove what is left after a short while.
• Use a wide, shallow dish in a quiet spot away from other pets.
• Offer food from your finger, or sit and stroke your cat while it eats.
• Try another texture. Some cats want a smooth loaf, others chunks in gravy, others dry.
• Ask before adding toppers. Many broths, gravies and meat baby foods contain onion or garlic, which are toxic to cats.
• Do not force feed. Syringe feeding without your vet's guidance can cause choking and a lasting dislike of food.

If the kidney diet is still refused, your vet will usually prefer that your cat eats a regular food it likes, with other measures to control phosphorus. Our article on why an old cat stops eating covers other causes, including dental pain.

What can you give a cat with kidney disease to gain weight?

Calories from a food the cat will reliably eat, and treatment for whatever is holding the appetite down. There is no single weight-gain food or supplement that does this safely on its own.

• Ask your vet to check for nausea, dehydration, constipation, dental pain, low potassium and anemia. Each one suppresses appetite and each can be treated.
• Feed more small meals across the day and evening.
• Ask whether a more calorie-dense kidney diet, or a prescription appetite stimulant, is suitable.
• Weigh your cat regularly on the same scale and share the numbers with your vet.

For a cat that cannot eat enough but still enjoys life, vets sometimes place a feeding tube. It sounds drastic, but many cats tolerate one well, and it takes the daily struggle out of food, water and medicine. Other causes of weight loss in old cats, such as an overactive thyroid, are worth ruling out too.

Bone broth for cats with kidney disease

Bone broth does not treat kidney disease, and there is no good evidence that it helps the kidneys. It is mostly water with very few calories, so a cat that fills up on broth may eat less real food.

Store-bought broths are a particular risk. Many contain onion or garlic, which are toxic to cats, and a lot of salt. The mineral content of homemade broth is unknown. If you want to use a little plain broth to tempt your cat or add fluid, clear the exact product or method with your vet first.

Natural remedies for kidney disease in cats

No herb, supplement or home remedy has been shown to treat or reverse kidney disease in cats. Lost kidney tissue does not grow back. Supplements are loosely regulated, some herbal products are hard on the kidneys or liver, and some interfere with prescribed medicines.

The measures with evidence are plain ones: the right food, enough water, blood pressure control and regular bloodwork. If you want to try a supplement, take the label to your vet before you give any.

Food recipes for cats with kidney disease

We do not publish one. When veterinary nutritionists have analyzed home-cooked kidney recipes from books and websites, most were missing essential nutrients. Cats are especially unforgiving here. They need taurine and other nutrients in precise amounts, and a shortfall can cause heart and eye disease.

A home-cooked kidney diet can be done, but it has to be formulated by a board-certified veterinary nutritionist for your cat's own bloodwork, with the supplements they specify, and adjusted as results change. Your vet can refer you.

When to call the vet today

• No food at all for 24 hours, or very little for two days
• Repeated vomiting, or vomit with blood in it
• Not drinking, or passing little or no urine
• Sudden weakness, wobbling, a drooping neck, collapse or hiding and not responding
• Sudden blindness, wide pupils or a seizure
• Drooling, pawing at the mouth or very bad breath that is new
• Your cat may have eaten onion, garlic, lilies or any human medicine

If eating has become a daily fight and other signs are piling up, a quality-of-life scale for senior cats can help you and your vet judge how your cat is really doing.

This article is general educational information about feeding cats with kidney disease, not veterinary advice. It intentionally gives no recipes, amounts or doses. Your cat's diet, and any phosphate binder, supplement, broth, appetite medicine or home-cooked food, should be chosen with your veterinarian based on your cat's bloodwork and stage of disease. A cat that stops eating should be seen promptly.