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Cat Kidney Disease Symptoms: Early Signs, Tests, Treatment

Drinking more, weight loss and bad breath can signal kidney disease in cats, but early signs are easy to miss. See what vets test, the four IRIS stages and how treatment works.

By Cat Care Store Editorial Desk7 min read
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The short answer: the early signs of kidney disease in cats are easy to miss. The classic ones are drinking and urinating more than usual, then weight loss, a poor appetite, vomiting, bad breath and a dull, unkempt coat. Cornell's Feline Health Center says many cats show no obvious signs at all in the early stages because the body compensates for lost kidney function. That is why a vet visit with blood and urine tests, not a guess at home, is how kidney disease is actually found. This guide is general information, not veterinary advice.

Who gets chronic kidney disease

Chronic kidney disease (CKD) is one of the most common illnesses of older cats. Cornell says it affects up to 40% of cats over 10 and 80% of cats over 15, and that age is the only known risk factor. It means the kidneys have lost function gradually and permanently: they filter waste from the blood, make urine and help regulate blood pressure, so when they struggle, the effects show up all over the body. If your cat is a senior, our guide to what changes to expect in a senior cat is a useful companion to this one.

Early signs: what you may notice at home

As the kidneys lose the ability to concentrate urine, cats make more of it and drink more to make up for it, according to Cornell. PDSA, the UK vet charity, lists the symptoms as peeing more, weight loss, vomiting, bad breath with a urine smell, and mouth ulcers. Putting the two together, here is what to watch for:

  • More drinking and bigger or more frequent urine clumps. You may notice the water bowl emptying faster, a cat drinking from taps or sinks, or litter clumps the size of fists. This is usually the first sign owners can spot.
  • Weight loss and less interest in food. Cornell notes that protein and vitamin loss in the urine can contribute to a poor appetite. Weigh your cat monthly; a slow slide is easy to overlook when you see the cat daily.
  • Vomiting, nausea or drooling. Waste products building up in the blood can make a cat feel sick.
  • Bad breath and mouth sores. PDSA lists breath with a urine smell and mouth ulcers.
  • A dull, unkempt coat and lethargy. Cornell says cats with built-up waste may look unkempt and tired.
  • Pale gums. CKD cats make less of the hormone that builds red blood cells, so anemia can develop, with lethargy, poor appetite and pale or white gums.

Not every sign means kidney disease. Thirst and weight loss also show up in diabetes and an overactive thyroid, and vomiting has dozens of causes. For a related picture, see our guide to the quiet ways cats hide illness, and if your cat has stopped eating, read what to do when a cat stops eating. A cat that is not eating for a day or more needs a vet.

When it is more urgent

Call your vet the same day if your cat is drinking and urinating much more than usual, vomiting repeatedly, hiding, very weak or refusing food. Go to an emergency clinic if your cat is collapsed, cannot stand, seems suddenly blind or disoriented, or may have swallowed something toxic. Cornell warns that high blood pressure, which affects roughly 60% of cats with CKD, can cause sudden vision changes, disorientation and weakness.

Kidney damage can also be sudden. The ASPCA lists the Easter lily as toxic to cats, with vomiting, lethargy and kidney failure among the possible signs, and notes that cats are the only species known to be affected. With bouquets arriving for the holidays, keep lilies out of any home with a cat, and call your vet or the ASPCA Poison Control line, (888) 426-4435, straight away after any contact.

How vets diagnose it

There is no single test, Cornell stresses. Your vet will usually run blood work and a urine test, and check blood pressure, because about 60% of CKD cats develop hypertension. A typical work-up looks at:

  • Creatinine, BUN and SDMA in the blood. Cornell says creatinine generally does not rise until a cat has lost almost 75% of kidney function, while SDMA rises when about 40% has been lost, so it can flag disease earlier.
  • Urine concentration (specific gravity). Weakly concentrated urine can be one of the earliest signs. A urine protein test shows how much protein is leaking.
  • A urine culture to rule out infection, and sometimes an ultrasound or X-rays.

Dehydration can make normal kidneys look bad on blood work, so Cornell says vets ideally want two samples taken within two weeks from a stable, well-hydrated cat. If you are weighing the cost of routine blood work for a senior cat, our article on dental cleaning costs explains why the pre-anesthetic panel is worth paying for, and choosing a vet covers how to ask for an estimate.

The four IRIS stages

The International Renal Interest Society (IRIS) stages CKD from 1 to 4 using blood creatinine and/or SDMA measured on at least two occasions in a stable cat, then adds sub-stages for protein in the urine and blood pressure. According to Cornell, cats diagnosed at stage 2 have a mean survival time of two to three years in many studies, while those first diagnosed at stage 4 survive less than six months on average. Those are averages, and individual cats vary widely, but the pattern is clear: the earlier the diagnosis, the more time there is to slow things down.

What treatment looks like

CKD has no cure, so the goal, in Cornell's words, is to slow progression and keep quality of life good. Your vet may combine:

  1. A kidney diet. Therapeutic diets restrict phosphorus, protein and sodium. Cornell says some studies found cats on a prescription kidney diet lived two to three times longer than cats on standard food, and that the diet is usually the first change recommended.
  2. Hydration. Wet food, several clean water bowls, a fountain if your cat likes one and, for advanced stages, fluids given under the skin, often at home every one to three days after training from your vet.
  3. Medication for related problems. Cornell names telmisartan for high blood pressure and protein loss, and says the oral drug molidustat is now available for anemia as long as blood pressure is controlled. Appetite stimulants and anti-nausea drugs can also help.
  4. Regular rechecks of blood, urine and blood pressure.

Dialysis and kidney transplants exist, but Cornell calls them complex, expensive and not proven in studies, so they are a specialist decision.

Will my cat eat the kidney food? New research

This is the part owners worry about most. A study published in the Journal of Veterinary Internal Medicine on October 7, 2026, and reported by Vet Candy on October 31, tested a commercial wet renal diet on 42 healthy cats in their own homes. Nearly 70% accepted it well (29 of 42), about 24% were reluctant, and when cats were offered both foods side by side, they ate similar amounts of each. The authors caution that all the cats were healthy and that cats with kidney disease often feel nauseous and eat less, so results may differ in real patients. The practical takeaways: introduce the new food gradually, treat nausea first if your vet suggests it, and match the texture your cat already likes. Never leave a CKD cat without food while it adjusts, because Cornell warns that short fasts can cause significant problems.

Can you prevent it?

Not entirely, because age is the only known risk factor. What you can do is catch it sooner: book a senior check-up every year (twice a year for older cats if your vet advises), ask for blood and urine tests that include SDMA, track weight and water intake, and keep toxins such as lilies and antifreeze away from your cat. If you have pet insurance, check how it handles chronic and pre-existing conditions before you need it. Our guide on whether pet insurance is worth it for cats explains what to look for. A urinary problem is a different emergency, covered in cat UTI symptoms.

Frequently asked questions

What are the first signs of kidney disease in cats?

Increased thirst and urination are usually first, followed by weight loss, reduced appetite, vomiting, bad breath and a poor coat. Many cats show nothing at first, so blood and urine tests are how vets find it early.

Can a cat recover from kidney disease?

Chronic kidney disease is progressive and cannot be cured, but treatment can slow it and many cats live comfortably for years. Sudden kidney injury, such as from a toxin, can sometimes be reversed if treated very quickly.

How long can a cat live with kidney disease?

It depends on the stage at diagnosis. Cornell cites mean survival of two to three years at IRIS stage 2 and under six months at stage 4, and stresses these are averages only.

Is drinking more water always a sign of kidney disease?

No. Diabetes, an overactive thyroid, heat and a salty or dry-food diet can also raise thirst. A persistent change is a reason to book a vet check.

What do vets test to diagnose it?

Blood tests (creatinine, BUN, SDMA), a urinalysis with urine concentration and protein, blood pressure, and sometimes imaging.

Sources

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