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Diabetes mellitus

Diabetes mellitus (DM) is also known as sugar diabetes and arises when the pancreas does not produce enough insulin. Insulin is the hormone which allows the cells in the body to utilize blood sugar (glucose) and as it’s level falls, blood sugar becomes raised, with many adverse side effects.


The most common cause of DM in cats is the destruction of the pancreatic cells responsible for insulin production, the beta cells. This normally results from chronic inflammation of the pancreas (chronic pancreatitis) and is known as Type I DM.

Type II DM, which arises from  resistance to insulin developing in the body cells, is unusual in cats

Clinical Signs

Most common in neutered male cats over 10 years of age

Clinical signs include weight loss, increased drinking and urination (PD/PU) and increased appetite.

Some cats also become lethargic and weak and may walk with their hocks (ankles) on the floor, due to potassium deficiency.

Diagnostic tests

DM is diagnosed when fasting glucose is significantly elevated (hyperglycaemia). Stressed cats can have a transient hyperglycaemia, so repeated blood glucose and the testing of urine for high glucose levels is needed to confirm the disease. Further confirmation can be obtained by testing a longer-lasting sugar in the blood, fructosamine.

Additional tests may be indicated to look for other disease that may accompany DM, such as liver disease, hyperthyroidism  and  urinary tract infections.


Cats with type II DM or mild Type I may respond to an oral mediaction (glipizide) which lowers blood glucose

Most cats require insulin injections to replace their body insulin deficit. There are different forms of insulin, each with a different duration of action. The most commonly used in cats are

Glargine (Lantus) – used increasingly as the first choice with a lower chance of lowering blood glucose levels to a dangerously low level (hypoglycaemia)

Protamine zinc insulin (PZI)- sometimes preferred as may be effective in some cats  given once daily

In addition to insulin, the diet may be changed to a low fat, high fibre diet available by prescription.

Follow Up Care and Monitoring

Diabetic cats can be difficult to monitor at home due to the necessity of regular collection of urine samples, and yet may become stressed and anorexic when hospitalised. As a result each case may be handled differently in a way best for that cat.

Most monitoring is by regular blood samples to check glucose levels in response to the current insulin dose.


Prognosis can be good if the DM can be regulated and stabilised.

Possible complications of DM include ketoacidosis and hypoglycaemic episodes.

 Effective communication between vet and owner is vital, and successful treatment requires that the owner learn to give insulin injections and become familiar with the signs of under and overdoseage.

With dedication from vet and owner many diabetic cats live active and happy lives for many years.