How Is Diabetes Diagnosed in Pets? Tests Explained

A diabetes diagnosis is usually straightforward, but it often takes more than a single test — and knowing why helps the process make sense.

What does the vet look for?

Diagnosis rests on two things together: persistently high blood glucose, and the typical signs (increased drinking, urinating, appetite and weight loss). One high reading alone isn't enough, because glucose can rise temporarily for other reasons — so vets confirm the pattern rather than acting on a single number.

Why is a stressed cat a special case?

Cats are the reason vets are cautious about one-off readings. A trip to the clinic can spike a cat's blood glucose from stress alone — "stress hyperglycaemia" — mimicking diabetes. To tell the difference, vets use a fructosamine test, which reflects average glucose over roughly the past week to ten days and isn't fooled by a single stressful morning.

What tests are typically run?

Commonly: a blood glucose measurement, a urine test (glucose spilling into urine is a strong clue, and it also screens for infection), and often a fructosamine test to confirm. Your vet may also check for ketones — substances that build up when diabetes is dangerously out of control — and run broader bloods to check for other conditions that often accompany diabetes.

What happens after diagnosis?

Your vet will start insulin and set up a plan to find the right dose over the following weeks, with rechecks. This settling-in period is normal and temporary. Keeping a clear record from day one makes those early adjustments faster and safer.

Mello helps you capture exactly the readings and notes your vet needs during this crucial early phase.

Sources

The pages below were each opened and checked before being listed here, and anything that could not be opened was left off rather than guessed at.

• Diabetes Mellitus in Dogs and Cats — MSD Veterinary Manual, reviewed May 2024, updated May 2026. That diagnosis rests on persistent high glucose together with glucose in the urine, and that fructosamine is normal where a rise was caused by stress.
• 2026 AAHA Diabetes Management Guidelines for Cats — American Animal Hospital Association, 2026. The point this page is named after: diagnosis needs sustained high glucose, documented more than once or in an unstressed or home setting. One high reading is not enough.
• 2026 AAHA Diabetes Management Guidelines for Dogs — American Animal Hospital Association, 2026. That glucose in the urine alongside high blood glucose establishes the diagnosis in dogs, and why ketones are checked early.
• ISFM Consensus Guidelines on the Practical Management of Diabetes Mellitus in Cats — Journal of Feline Medicine and Surgery 17(3):235–250, 2015. Repeat testing to confirm, and fructosamine as the measure less disturbed by short-term stress.