Glossary

Diabetes mellitus

A disease in which the body cannot make or use enough insulin, so blood sugar stays high, with increased thirst and urination.

Also called: diabetes, canine diabetes, sugar diabetes, diabetic dog

Diabetes mellitus means the body cannot move sugar from the blood into cells because insulin is lacking or not working. Most diabetic dogs lack insulin, so they usually need lifelong management that a vet designs, including regular meals and monitoring.

Early signs are drinking more, urinating more, weight loss despite a good appetite and tiredness. Cataracts can develop quickly in diabetic dogs. It is most often diagnosed in middle-aged and older dogs, and unspayed females and overweight dogs are at higher risk.

A dog that is vomiting, weak or very lethargic may be in diabetic ketoacidosis, which is an emergency. Diabetes is different from the less common diabetes insipidus, which involves water balance rather than sugar. Always have a vet test blood and urine before assuming a thirsty dog is diabetic.

Last reviewed November 8, 2026

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Related terms

Pancreatitis Inflammation of the pancreas that causes vomiting, belly pain and loss of appetite, and can range from mild to life-threatening. Obesity Excess body fat that shortens lives and raises the risk of arthritis, diabetes and other disease; it is the most common nutrition problem in pet dogs. Cataracts Cloudiness in the lens of the eye that blocks light and can lead to blindness, often inherited or linked to diabetes. Cushing's disease A hormone disorder in which the body makes too much cortisol, usually in middle-aged and older dogs, causing thirst, a pot belly and thin skin.