Updated September 25, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: Not every senior cat needs a renal (kidney) diet. Healthy older cats often need more protein, not less, to hold on to muscle. A renal diet is recommended once bloodwork and urine tests confirm chronic kidney disease (CKD), usually from IRIS stage 2 onward. For those cats, it’s the treatment with the strongest evidence for longer survival. The key first step is testing, not switching food on a guess.
Kidney disease is common in older cats
CKD affects a large share of cats over 10, and even more over 15. Early signs are easy to miss:
- Drinking more and urinating more (bigger litter clumps)
- Gradual weight and muscle loss
- Pickier appetite, occasional vomiting
- A dull or unkempt coat
Get tested first
Senior cats should have checkups at least yearly, and many vets recommend every 6 months. Tests for kidney health include:
- Creatinine and SDMA blood tests
- Urine concentration (urine specific gravity) and protein in the urine
- Blood phosphorus and potassium
- Blood pressure
- Thyroid level: hyperthyroidism is also common in seniors and can hide kidney disease until it’s treated
If your senior cat is healthy
- Feed a complete, balanced diet with plenty of high-quality protein. Many seniors lose the ability to digest protein and fat as efficiently.
- Choose wet food or add water to meals for hydration.
- Avoid very high-phosphorus treats like jerky and cheese.
- Watch weight and muscle, and recheck bloodwork as your vet advises.
If your senior cat has kidney disease
A prescription renal diet lowers phosphorus, provides moderate high-quality protein, and adds omega-3s, potassium, and B vitamins. In a two-year controlled trial, cats with stage 2–3 CKD eating a renal diet had fewer kidney crises and kidney-related deaths. Several companies make prescription renal diets in wet and dry forms, so there’s room to find one your cat likes. Read more in our guide to the feline kidney support diet.
Senior cats with more than one condition
- Hyperthyroidism plus CKD: your vet will balance treatment of both. Iodine-restricted thyroid diets and renal diets can’t always be combined.
- Diabetes plus CKD: diet choice needs to account for both carbohydrate and phosphorus.
- Muscle loss or poor appetite: keeping your cat eating comes first. Your vet may prescribe anti-nausea medication or an appetite stimulant.
Switching safely
- Transition over 2–3 weeks or longer, mixing more of the new food each day.
- Don’t start a new diet while your cat is nauseous or hospitalized, which can cause a lasting food aversion.
- Warm wet food slightly to make it more appealing.
- If your cat refuses renal diets, a vet-recommended lower-phosphorus food plus a phosphate binder is a reasonable fallback. A cat eating something is always better than a cat eating nothing.
What to avoid
- Cutting protein in a healthy senior “to protect the kidneys.” There’s no evidence it prevents CKD, and it can speed muscle loss.
- Homemade kidney diets from the internet: most are unbalanced. Use a recipe from a board-certified veterinary nutritionist. See our homemade renal diet guide.
- Mixing in regular food or treats that undo phosphorus restriction.
Frequently asked questions
At what age should a cat go on a kidney diet?
Age alone isn’t the trigger. A kidney diet is recommended when tests show CKD, typically IRIS stage 2 or higher.
Can I feed a renal diet to my other, healthy cat?
It’s not designed for healthy cats. In multi-cat homes, microchip feeders or separate feeding rooms help each cat eat its own food.
Wet or dry renal food?
Wet is usually better for the extra water, but the best food is one your cat will eat consistently.
Sources
- International Renal Interest Society (IRIS): Staging of CKD and treatment recommendations
- Ross SJ, et al. Clinical evaluation of dietary modification for treatment of spontaneous chronic renal failure in cats. JAVMA. 2006
- AAFP/AAHA Feline Life Stage Guidelines. J Feline Med Surg. 2021
- Laflamme D, Gunn-Moore D. Nutrition of aging cats. Vet Clin North Am Small Anim Pract. 2014
- Cornell Feline Health Center: Chronic kidney disease
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.