Why does my cat's urine smell so strong? 6 UK causes and when to worry.

Cat urine has always been pungent — that's the ammonia content. But a sudden change in smell, or a new sharpness that wasn't there before, is one of the most reliable early signals of urinary disease that UK owners actually notice. Here are the six most common causes.

1. Concentrated urine from dehydration

The most common cause. Cats are notoriously poor drinkers. Concentrated urine smells stronger and looks darker. Add a fountain, switch to wet food, and the smell typically softens within days.

2. Urinary tract infection (UTI)

A UTI changes urinary pH and adds bacterial byproducts — the result is a sharper, more medicinal ammonia smell. On a colour-changing health litter the same shift turns the crystals blue or green. Book a vet appointment within 24–48 hours.

3. Marking by an unneutered male

Intact male spray smells dramatically stronger and more musky than normal urine. Neutering resolves it in roughly 90% of cases within weeks.

4. Kidney disease

Counterintuitively, cats with CKD often produce more dilute urine that initially smells weaker — but as toxins build, owners frequently report a sweet or chemical-tinged ammonia smell. Pair with increased thirst and urination volume to flag.

5. Feline diabetes

Diabetic urine sometimes smells faintly sweet or fruity due to glucose and ketones. If you notice this alongside increased thirst and weight loss, ask your vet for a blood glucose check.

6. Diet change or supplements

High-protein diets, taurine supplements and some prescription foods can shift urine smell. If the change matches a recent food switch, give it 1–2 weeks before worrying.

When to call your UK vet

Call within 24–48 hours if a smell change is paired with: more or less litter tray usage, blood, straining, weight loss, or increased thirst. Same day if your cat is straining and producing little or no urine — especially in a male cat.

How to monitor cat urine smell and chemistry at home

Smell alone is subjective. The objective version is colour-changing crystal litter, which reads pH and blood chemistry directly. Kittydoctor turns the litter tray into a daily report card — yellow/olive normal, orange acidic, blue/green alkaline (UTI), red blood — for £34.99 per 60-day supply.