Chronic Kidney Disease: The Numbers Every Cat Owner Should Know
By the time the classic signs appear, most of the function is gone. The case for screening earlier, and what to actually ask your vet for.
Chronic kidney disease is the condition most likely to kill your cat if it lives long enough. Prevalence estimates vary by population and method, but the broad picture is consistent: it is common in cats over ten, and substantially more common again in cats over fifteen.
The problem with waiting for symptoms
The classic presentation — drinking more, urinating more, losing weight, a dull coat — tends to appear only once a large share of functional kidney tissue is already gone. Cats compensate well and hide decline. An owner watching carefully at home will usually notice something, but late.
This is why the argument for routine screening in older cats is strong. You are not looking for a cure; there is not one. You are looking for the point at which diet, blood pressure control and phosphate management still have years to work with.
What to ask for
Urine specific gravity. Concentrating ability falls early. A dilute urine sample in a cat that is not on fluids or diuretics is a real signal, and it is cheap to check.
SDMA. A blood marker that tends to rise earlier in the course of disease than creatinine does, and is less affected by muscle mass — which matters in an old, thin cat.
Creatinine and urea, read together with the urine result. Creatinine alone, in isolation, is a weaker test than most owners assume.
Blood pressure. Hypertension is common alongside kidney disease and causes separate, avoidable damage — including sudden blindness from retinal detachment.
Urine protein-to-creatinine ratio. Protein loss is associated with faster progression and is treatable.
Staging is not a formality
The International Renal Interest Society stages kidney disease from 1 to 4, with substaging by protein loss and blood pressure. The stage changes the treatment, not just the prognosis conversation. Ask which stage your cat is in and what would move it.
What actually changes outcomes
A renal therapeutic diet — lower in phosphate, with modified protein and added omega-3s — has the best evidence of anything on the list for extending survival in cats already in the middle stages. Phosphate binders are added when diet alone does not hold the numbers. Blood pressure medication, where indicated, protects the eyes, heart and kidneys at once.
Hydration is supportive, not curative — but it is the piece owners control every day. See our guide to water for the practical version.
The part nobody tells you
Kidney disease in cats is usually slow. A cat diagnosed at stage 2 with good management may have years of ordinary life left. The diagnosis is not the end of the story, and the owners who do best are the ones who get it early enough to have options.
This article is general information and is not a substitute for examining your cat. Anything here that sounds like your cat is a reason to book an appointment, not a reason to self-treat.
This is general information, not a diagnosis.
Every cat is a specific animal with a specific history. Use this to ask your vet better questions — not to replace the examination. Spotted an error? Tell us and we will correct it in public.
