Diabetes mellitus
Also called Sugar diabetes
A lifelong disease in which the body does not make or use enough insulin, so blood sugar rises and spills into the urine. It is most common in middle-aged dogs and middle-aged to older cats.
Cause and spread
- Cause
- Loss of insulin-making cells (from immune damage or pancreatitis in dogs, amyloid in cats) and insulin resistance, increased by obesity.
- How it spreads
- It is not infectious.
Signs to watch for
- Increased thirst and urination
- Increased appetite with weight loss
- Weakness and lethargy
- Cataracts in dogs
- Vomiting and collapse if ketoacidosis develops
Many diseases look alike. Only a laboratory test can tell them apart, so please see a veterinarian for any sick animal.
How it is diagnosed
Diagnosis needs persistent high blood sugar together with sugar in the urine. In cats, stress alone can raise blood sugar, so more than one sample may be needed and a fructosamine test can help tell the two apart.
Prevention and control
- Keep pets at a healthy weight
- Have middle-aged and older pets checked regularly
- Follow your veterinarian's insulin and diet plan, with regular glucose checks
Where this information comes from
- Diabetes Mellitus in Dogs and Cats · Merck Veterinary Manual
General information for animal owners and veterinarians, last checked October 2026. It does not replace the advice of your veterinarian, who should decide which tests and treatment your animal needs.