What chronic kidney disease is and how to spot it in cats
Chronic kidney disease (CKD) is a slow, long-term loss of kidney function that develops over months or years. Unlike acute kidney injury — a sudden insult that can sometimes be reversed — CKD is progressive and, per the Cornell Feline Health Center, “a progressive disease with no definitive cure.” The goal of treatment is to slow it down, not undo it. CKD is also one of the most consequential illnesses of feline aging: the Cornell Feline Health Center reports it affects up to 40% of cats over age 10 and up to 80% of cats over age 15, making it the leading medical cause of death in older cats.
The cruel part is that CKD is nearly silent early on. Cats are born with far more kidney capacity than they need, so outward signs usually appear only after substantial function is already lost. According to the Merck Veterinary Manual, the earliest practical signs are excessive thirst and urination, which is why a senior cat suddenly emptying the water bowl deserves attention. As the disease advances, the Cornell Feline Health Center notes you may see loss of appetite, weight loss, lethargy, and an unkempt or greasy coat; the Merck Veterinary Manual adds vomiting, dehydration, mouth sores, and bad breath. None of these signs is specific to CKD — which is exactly why they call for testing rather than guesswork.
What causes CKD in cats
In most cats, CKD is simply a disease of getting older. The Merck Veterinary Manual states that most of the time the cause is related to old age, with the kidneys gradually wearing out their filtering units over a lifetime. This is also where the feline picture differs sharply from dogs: CKD is dramatically more common in cats than in dogs, and the contrast widens with age. For worried owners, that means a senior cat is in a genuinely higher-risk group than a senior dog, and routine screening matters more.
When a specific underlying cause can be found, the Merck Veterinary Manual points to several: circulatory problems such as high blood pressure, and other kidney conditions including pyelonephritis (kidney infection), obstruction from urinary stones, and tumors. A minority of cases are inherited or congenital, and certain breeds are predisposed. Importantly, some causes are external and preventable — nephrotoxins like certain medications and plants can damage kidneys directly. Whatever the trigger, once enough functional tissue is lost the remaining kidney is left working harder, which tends to drive further decline over time.
Diagnosis, IRIS staging, and when to see your vet
CKD is diagnosed with a combination of blood and urine tests, not a single number. The Cornell Feline Health Center describes the core blood markers as creatinine, BUN (blood urea nitrogen), and SDMA — a newer marker that, per Cornell, becomes detectable when about 40% of kidney function is lost, compared with roughly 75% loss before creatinine rises. That earlier warning is why SDMA is so useful. Urine testing adds urine specific gravity (how well the kidneys concentrate urine) and the urine protein-to-creatinine ratio, and the Merck Veterinary Manual notes blood pressure should also be measured.
Once CKD is confirmed, vets stage it using the IRIS (International Renal Interest Society) system. Per IRIS, stable patients are placed into Stages 1 through 4 based on fasting blood creatinine and/or SDMA, then sub-staged by proteinuria and blood pressure — and that stage is what drives the treatment plan. Because CKD is silent early, the strongest move is screening before signs appear: have senior cats checked with bloodwork and a urinalysis on the schedule your vet recommends. See your veterinarian promptly if your cat is drinking or urinating noticeably more, losing weight or appetite, vomiting, or seeming run-down — and treat sudden collapse, not eating, or any lily exposure as an emergency.
The diet connection: what a renal diet can and can’t do
Diet is the single best-evidenced intervention for feline CKD — the star of the treatment plan, not a footnote. In a double-masked, randomized controlled trial of 45 cats with stage 2 or 3 CKD, Ross and colleagues (JAVMA, 2006) found that 26% of cats on a standard maintenance diet had uremic episodes versus 0% on a therapeutic renal diet, along with a significant reduction in renal-related deaths. The leading lever is reduced phosphorus, which the evidence consistently ties to slower progression. Just as important is controlled, high-quality protein: a renal diet moderates protein, but it is emphatically not a no-protein diet — cats are obligate carnivores and starving them of protein causes harmful muscle loss.
A good therapeutic renal diet, as described by the Cornell Feline Health Center, is restricted in phosphorus, protein, and sodium and supplemented to support the failing kidney, often including added omega-3 fatty acids and potassium with buffering against acidosis. Because hydration protects the kidneys, vets generally favor wet food and multiple water sources to keep cats drinking. What a renal diet cannot do is cure or reverse CKD — it slows the disease and improves quality of life. If you are weighing specific products, our guide to the Best Cat Food for Kidney Disease breaks down what to look for, but the diet should always be matched to your cat’s IRIS stage with your vet.
Managing CKD day to day — and what to avoid
Beyond diet, managing CKD means partnering with your vet on the complications that come with it. The Cornell Feline Health Center notes that CKD cats commonly develop high blood pressure and anemia, both of which have treatments, so periodic rechecks of bloodwork, blood pressure, and urine are part of normal care. Keeping a CKD cat eating is a priority in itself: appetite is fragile, so introduce any new food gradually over one to two weeks, and tell your vet quickly if your cat stops eating rather than waiting it out. In advanced stages, supplemental fluids given under the skin can help, as the Cornell Feline Health Center describes.
Some things are worth actively avoiding. Skip NSAIDs and other potential nephrotoxins unless your vet specifically prescribes them, and never give human pain relievers. Don’t attempt extreme do-it-yourself protein restriction — over-restricting protein backfires by wasting muscle. And keep lilies out of any home with a cat: per the ASPCA and FDA, true lilies are acutely toxic to cats, every part of the plant including the pollen and vase water is dangerous, and even a tiny exposure can cause sudden kidney failure. Any known or suspected lily contact is a same-day emergency — call your vet or an animal poison control line immediately.
Frequently asked questions
Is chronic kidney disease in cats curable?
No. According to the Cornell Feline Health Center, CKD is a progressive disease with no definitive cure. The aim of treatment is to slow how fast it advances and to keep your cat feeling well, which is achievable for many cats over a meaningful period. That is also why early detection matters so much.
What is usually the first sign of kidney disease in a cat?
The earliest practical sign most owners notice is increased thirst and urination, per the Merck Veterinary Manual. CKD is largely silent before that point because cats have so much kidney reserve. If your cat is suddenly drinking more, losing weight, or eating less, it is worth a vet visit and bloodwork.
Does a special kidney diet really help, or is it marketing?
It genuinely helps and is the best-evidenced treatment. In a randomized controlled trial by Ross and colleagues published in JAVMA in 2006, cats with stage 2 or 3 CKD fed a therapeutic renal diet had fewer uremic crises and fewer kidney-related deaths than cats on a standard diet. The diet works mainly by reducing phosphorus while still supplying high-quality protein, so it slows the disease rather than curing it.
For diet-side context, see Best Cat Food for Kidney Disease, Best Cat Food for Senior Cats, Omega-3 Fatty Acids, Explained. To check whether your cat’s food matches the rubric criteria discussed above, paste the ingredient list into the KibbleIQ analyzer. For scoring methodology context, see our published methodology.
Related condition deep-dives: Hyperthyroidism in Cats · FLUTD in Cats.