Last Updated: 06/08/2026
Kidney Disease in Cats: A Complete Guide to CKD
Kidney disease affects up to 40% of cats over 10. Learn the early signs to watch for, IRIS stages 1-4 explained in plain English, and what treatment involves.
Author: Dr Gillian Hill BVSc (Hons)
Reading Time: 4 minutes - short read
Chronic kidney disease (CKD) is one of the most common conditions in senior cats, affecting an estimated 30-40% of cats over the age of 10, and is staged from 1-4 using the International Renal Interest Society (IRIS) guidelines based on blood creatinine and SDMA levels.
If your cat has just been diagnosed with chronic kidney disease, or you've noticed some worrying changes before your vet appointment, you're in the right place.
A CKD diagnosis can feel overwhelming, but here's what's important to know upfront: this condition is very manageable, and with the right care, many cats go on to live comfortable, happy lives for years after diagnosis.
What is chronic kidney disease in cats?
The kidneys filter waste from the blood, regulate hydration, and produce hormones that support red blood cell production and blood pressure. Kidney disease (CKD) is a progressive condition where this filtering capacity declines gradually, usually over months to years, until waste starts building up in the bloodstream.
What makes CKD particularly sneaky is that cats don't show obvious signs until around two-thirds of kidney function is already lost. By the time symptoms appear, the kidneys have been quietly struggling for a while.
You might also hear it called kidney failure or renal failure - these terms are often used interchangeably, though CKD covers the full spectrum from early-stage disease through to the severe end.
Why are cats so prone to kidney disease?
CKD affects an estimated 30-40% of cats over 10. While kidney disease affects dogs too, cats are unusually vulnerable for a few reasons: they evolved with a naturally low thirst drive, so they can be chronically mildly dehydrated. Their kidneys also process a high-protein diet throughout their lives, accumulating wear over time.
Cats also have a much smaller pool of filtering units/nephrons (about 200,000 per kidney, compared to 400,000 in dogs and about 1,000,000 in humans). This means that the loss of nephrons pushes them closer to kidney failure much faster than it would for other species. Conditions like hyperthyroidism, dental disease, high blood pressure, and recurrent urinary tract infections can also contribute to kidney damage if left unmanaged.
What are the signs of kidney disease in cats?
Early signs are easy to dismiss as normal ageing. Watch for:
- Increased drinking and urination: often the first clue, as damaged kidneys lose the ability to concentrate urine. If you've noticed your cat at the water bowl more than usual, see our guide on why cats drink more water
- Gradual weight loss is one of the subtler early signs of CKD - if your senior cat is dropping weight, read our guide to weight loss in senior cats for more info on what else could be going on.
- Reduced appetite and leaving food unfinished
- Dull or unkempt coat
As CKD progresses, symptoms become harder to miss: vomiting, bad breath with a distinctive ammonia-like smell, lethargy, muscle wasting along the spine, and pale gums. If you're seeing any of these in a cat aged 7 or older, an urgent vet visit is important.
What is IRIS staging for CKD in cats?
Your vet will use the IRIS (International Renal Interest Society) guidelines to stage CKD based on blood creatinine and SDMA levels:
- Stage 1 (Early): Mildly reduced kidney function, usually no symptoms. Often picked up on routine senior blood or urine tests.
- Stage 2 (Mild): Where most cats are at first diagnosis. May be drinking and urinating more than usual. Treatment (primarily diet) usually begins here.
- Stage 3 (Moderate): Significant kidney dysfunction, often with noticeable symptoms. More active management required, including medications and sometimes home fluid therapy.
- Stage 4 (Severe): Minimal kidney capacity. Focus shifts to comfort and quality of life.
Your vet will also substage based on blood pressure and protein in the urine - both of which accelerate damage if untreated.
How is kidney disease in cats treated?
Diet is the single biggest lever. Kidney-specific prescription diets reduce phosphorus (which drives kidney damage when it can't be cleared) and moderate protein waste, and they encourage more fluid intake through wet food formats. Studies show these diets can slow CKD progression significantly.
See our guide to the best food for cats with kidney disease for a full breakdown. For a deep dive on Hill's k/d specifically, see our Hill's partnership guide to how nutrition can support your cat's kidney health.
Beyond diet, most cats with moderate to advanced CKD also need medications and supportive care - including phosphate binders, anti-nausea medications, blood pressure management, and home subcutaneous fluids. Our managing CKD in cats guide covers each of these in detail, including giving fluids at home and when to consider palliative care.
CKD is common in senior cats, but it's one of the most manageable chronic conditions in feline medicine. The earlier it's caught, the more you can do. Watch for increased thirst and urination, especially in any cat over 7, and push for routine senior bloods if you haven't already. With the right diet and a monitoring plan from your vet, many cats with CKD live comfortably for years.
References
Ross SJ, Osborne CA, Kirk CA, et al. (2006). Clinical evaluation of dietary modification for treatment of spontaneous chronic kidney disease in cats. Journal of the American Veterinary Medical Association, 229(6), 949-957. https://doi.org/10.2460/javma.229.6.949. Accessed August 2026.
International Renal Interest Society (IRIS). (2023). IRIS Staging of CKD (modified 2023). Retrieved August 2026 from http://www.iris-kidney.com/guidelines/staging.html
Sparkes AH, Caney S, Chalhoub S, et al. (2016). ISFM Consensus Guidelines on the Diagnosis and Management of Feline Chronic Kidney Disease. Journal of Feline Medicine and Surgery, 18(3), 219-239. Accessed August 2026.
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History
Our experts continually monitor the health and wellness space and we update our articles when new information becomes available.
Wed 5 Aug 2026
Written by Dr Gillian Hill BVSc (Hons)Dr Gillian Hill BVSc (Hons)
Veterinarian
Dr. Gillian graduated from the University of Sydney in 2005 with a Bachelor of Veterinary Science. She worked in a number of small animal clinics, before joining the Pet Circle Vet team in 2020. Dr. Gillian has special interests in ultrasonography, surgery and behaviour. Her favourite part of being a vet is being an advocate for the animals. She loves helping owners to make the best, evidence-based decisions for their pets, and seeing the beautiful bond that people have with their fur-babies.
