Blood Glucose (GLU)

What it measures

Glucose is the body's main energy source. It comes from food, is stored and made by the liver, and is regulated by insulin. A persistently high glucose is the main feature of diabetes, but glucose is also easily affected by short-term factors such as meals and stress.

What a high value may mean

Possible causes include a recent meal; stress or excitement (an adrenaline-driven rise usually lasts 4 to 6 hours, while a rise driven by stress hormones can last several days); diabetes; other hormone diseases; and some drugs. Cats are especially prone to stress hyperglycemia at the vet and may even show temporary glucose in the urine, so a single high blood or urine glucose cannot confirm diabetes.

What a low value may mean

Possible causes include a sample that was not processed in time (blood cells keep using up glucose, causing a false low); an insulin dosing problem; xylitol eaten by a dog; a long time without food; severe infection; poor liver function; and some tumors (such as insulinoma in dogs).

Usually read together with

A urine test (glucose and ketones), fructosamine, and liver values. Fructosamine reflects average glucose over a period of time and helps tell true diabetes from short-term stress; however, research shows that even with very high glucose, it takes about 3 days for fructosamine to rise in cats.

When to follow up

If your cat drinks more, urinates more, and loses weight despite eating a lot, along with high glucose, follow your vet's plan for confirmation tests such as fructosamine or a urine test. If a cat on insulin has a low glucose reading, contact your vet directly and do not change the dose on your own.

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