What causes diabetes mellitus in cats

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Cat Resting on Blanket
Cat Resting On Blanket

Diabetes in cats is a common disease that involves the feline endocrine system. In fact, it is the second most common endocrine disease seen in cats.

What Diabetes Mellitus Is

Diabetes mellitus is a disease that revolves around the excretion of insulin by the pancreas and the ability of that insulin to properly regulate the blood glucose (blood sugar) levels.

Insulin is necessary for all animals (and people) to regulate the level of glucose, or sugar, in the blood. When the pancreas is unable to produce insulin in adequate amounts or the body is unable to properly use that insulin, the blood glucose level increases above normal levels and diabetes mellitus results.

grayscale photo of cat with yellow eyes
grayscale photo of cat with yellow eyes


Essentially, there are three different classifications of diabetes mellitus.

  • Type I Diabetes Mellitus: Type 1 is insulin-dependent, meaning that the pancreas of the diseased animal (or person) can no longer produce adequate amounts of insulin.
  • Type II Diabetes Mellitus: Type 2 is non-insulin-dependent and occurs when the body is not able to utilize the insulin that is produced in an efficient fashion. In these cases, the pancreas is still able to produce insulin, at least to some degree.
  • Type III Diabetes Mellitus: Type 3 involves insulin interference by certain diseases, conditions and/or drugs. Examples include hyperadrenocorticism (Cushing's disease), acromegaly, gestational diabetes and diestrus (part of the reproductive or heat cycle of the cat).

Feline diabetes mellitus differs drastically from diabetes mellitus in dogs. Dogs with diabetes almost always suffer Type I diabetes. However, cats more often are diagnosed with Type II diabetes, at least in the early stages of the disease.

grey tabby cat beside short-coat brown and white dog
grey tabby cat beside short-coat brown and white dog

In the early stages of feline diabetes, it is possible for a cat to go into remission and be able to regulate blood glucose again if treatment is instituted before severe damage to the pancreas occurs.

If diabetes is left untreated for the cat, eventually the stress on the pancreas as it tries to produce more insulin in response to continually elevated blood glucose levels will lead to the destruction of the pancreatic cells. When this happens, the disease will revert to Type I diabetes and the cat may become dependent on insulin injections.


Feline diabetes mellitus may be caused by amyloidosis, pancreatitis, or by certain drugs. Amyloidosis is a disease in which amyloid, a starch-like protein, is deposited into the pancreas and sometimes other body tissues. Pancreatitis is an inflammation of the pancreas. Drugs that may cause diabetes include corticosteroids and megestrol acetate.

brown tabby cat
brown tabby cat

Obesity is also a significant factor in the development of diabetes mellitus in cats.


Diabetes mellitus tends to occur most often in middle-aged cats though it is possible to see the disease in younger cats as well.

The signs most commonly seen in cats with diabetes mellitus include:

brown tabby cat sitting on front of glass window
brown tabby cat sitting on front of glass window
  • Increased urination
  • Increased thirst
  • Increased hunger
  • Weight loss
  • Muscle weakness

Diabetic cats may also develop a neuropathy in which the hind legs become weakened and the cat takes on an abnormally flat-footed stance and gait on the hind legs.

Cataracts, though relatively common in dogs with diabetes, do not often occur in diabetic cats.

Diabetes mellitus in cats may start off being Type II (or non-insulin-dependent) and some cats may be able to attain a state of remission if treated properly early in the disease. Left untreated, feline diabetes will likely become insulin-dependent.