Cat Urinary Diets Explained: Struvite, Crystals and Prescription Food

By Tailwisp Editorial TeamUpdated October 20, 20264 min read

Few feline problems cause as much discomfort and expense as urinary disease. Crystals, stones and inflammation of the bladder can make a cat strain, cry in the litter box or urinate in strange places. Diet is one of the main tools vets use, both to treat existing problems and to stop them coming back. This guide explains how urinary diets work, and how to use them well.

Why diet affects the urinary tract

Urine is a solution of water and dissolved minerals. If it is too concentrated, or has the wrong pH, minerals can form microscopic crystals, which may clump into stones or plug the urethra. The two most common types in cats are struvite and calcium oxalate. Food influences three things: how much water the cat takes in, how acidic or alkaline the urine is, and how many minerals are available to form crystals. See bladder stones and crystals in cats.

How urinary diets work

• Controlled minerals. Magnesium, phosphorus and calcium are kept within limits that discourage crystal formation.
• Urine pH management. Struvite crystals form in alkaline urine, so struvite diets acidify urine slightly. Calcium oxalate forms in acidic urine, so those diets avoid over-acidifying.
• Increased urine volume. Higher sodium levels in some foods encourage drinking, and wet formulas provide water directly. Dilute urine is hard for crystals to form in.
• Dissolution. Some diets can dissolve struvite stones in a few weeks, under veterinary monitoring.

Struvite versus calcium oxalate

Struvite stones can often be dissolved with diet. Calcium oxalate stones cannot be dissolved, and usually need surgical removal, followed by diet and water strategies to prevent new ones. Your vet identifies the type from urine tests, X-rays or ultrasound, and sometimes by analyzing a stone. Never choose a urinary diet without knowing which problem your cat has.

Feline idiopathic cystitis

Many cats with bladder inflammation have no crystals or stones. This is called idiopathic cystitis, and stress plays a major role. Increasing moisture, using urinary or stress-support diets and reducing stress all help. See feline idiopathic cystitis and urinary tract infection in cats.

Who needs a urinary diet?

• Cats diagnosed with struvite crystals or stones.
• Cats with recurrent cystitis, as advised by a vet.
• Cats that have recovered from a urinary blockage, particularly males.
• Cats with calcium oxalate stones, on an appropriate preventive formula.

Healthy cats do not need them. Using a urinary diet without a reason can cause problems if it has unsuitable mineral levels, particularly in kittens or cats with other conditions.

Water is the main event

No food works well unless the cat drinks and eats enough moisture. Tactics include:

• Feed wet food, at least in part. Canned urinary diets are generally preferred.
• Add water to food.
• Offer a fountain, and several bowls in different places. See how to get a cat to drink more water.
• Keep bowls clean and wide, so whiskers are not squeezed.
• Add a splash of low-sodium broth if your vet permits.

Emergencies

A male cat that strains, produces little or no urine, cries or hides may have a urethral blockage, which can kill within a day or two. This is an emergency. Do not wait to see if diet helps. See signs of a urinary blockage in cats.

Using a prescription urinary diet

1. Get a diagnosis from your vet, with a urinalysis.
2. Choose the diet your vet recommends. Many are prescription-only. See prescription cat diets explained.
3. Transition gradually, over a week or so, unless dissolving stones, in which case follow your vet's timeline. See how to switch cat foods.
4. Feed it exclusively. Treats, other foods and supplements can undo the effect. Check treat options with your vet.
5. Recheck urine as scheduled, often after two to four weeks, then periodically.
6. Stay consistent. Stopping early can allow crystals to return.

Multi-cat homes

Make sure only the affected cat eats the urinary diet, using separate rooms or microchip feeders. See feeding cats in a multi-cat home.

Stress and the litter box

Stress is a trigger for cystitis. Keep litter boxes clean, give hiding spaces, keep routines steady and provide play. See why is my cat peeing outside the litter box and blood in cat urine.

Over-the-counter urinary foods

Some non-prescription foods are labeled as urinary or urinary tract health. They may help maintain a healthy urinary tract, but they are not the same as treatment, and are not proven to dissolve stones. Ask your vet before relying on them.

Costs and expectations

Prescription urinary diets cost more than ordinary food, but they cost far less than a blockage emergency. Many cats accept them well, and some need a gradual introduction or a different brand.

When to see a vet

See a vet if your cat strains, visits the litter box often, passes blood or cries when urinating. Use the US vet directory to find a clinic, and treat any suspected blockage as an emergency.

This article is general educational information, not veterinary advice. Every cat is different. If your cat is unwell, or you are unsure about a symptom, diet change or medication, contact your veterinarian.