Feline Diabetes Mellitus


Diabetes mellitus is a failure to regulate blood sugar levels. In normal animals insulin is produced by the pancreas gland to control cell uptake and metabolism of glucose. Without insulin, cells are starved of energy and the body starts to break down fat and protein as alternative energy sources. Excess glucose circulating in the blood cannot be utilised. Its excretion by the kidneys causes loss of large amounts of fluid, causing increased urination and consequently increased thirst. Diabetes mellitus can occur either as failure of the pancreas gland to produce sufficient insulin or as a resistance of tissue cells to insulin. In cats there are three main types of diabetes mellitus:

Type I (Insulin-dependent) diabetes mellitus

These cats are usually thin and often develop ketoacidosis, a life threatening condition arising from the breakdown of fat stores and inability to utilise glucose. Lifelong insulin treatment is required.

Type II (Non-Insulin dependent) diabetes mellitus

These cats are often obese and do not develop ketoacidosis. Insulin therapy may help, but is not essential for survival.

Type III (Secondary diabetes)

Diabetes may result from other diseases such as primary pancreatic disease, hormonal diseases or endocrinopthies, or from drug therapy.


Affected cats are usually middle-aged to older animals and are more likely to be female than male. Increased urination and thus increased drinking are the primary features. Some cats have an increased appetite. Muscle wastage, dehydration and weight loss may be seen. Diagnosis is based on persistently elevated blood glucose levels and glucosuria (glucose in the urine).


For the owner, there are two implications: financial and personal commitment. Treatment of a Type I diabetic cat requires maintenance of a daily treatment plan, with careful attention to timing of feeds and administration of insulin. Most cats require twice daily insulin injections. Once well-regulated, maintenance costs are minimal. However, initial stabilisation is expensive and complications may arise. In the initial stabilisation period, hospitalisation is often necessary and is essential if ketoacidosis has developed. Regular return visits will be required to monitor progress, particularly in the first few months.


Consistency! – Same food, same time, same insulin and a stable stress-free lifesytle. This will be much easier if the cat leads an indoor life. If insulin is to be administered twice daily, two equal meals should be given just prior to injection, for instance at 8.00 a.m. and 8.00 p.m. Insulin injections are not painful. Needles are tiny and injected volumes are very small. They are given in the scruff of the neck, just beneath the skin. Insulin needs to be kept refrigerated and should be mixed thoroughly but gently prior to use.

Special veterinary diets are also available that can aid stabilisation of the disease and in some cases reduce the insulin requirement.

Home monitoring

You must be aware of appetite, weight, and water consumption. Any significant change is an indication that the diabetes is not well controlled and veterinary advice should be sought. In the event of not eating, veterinary advice should be sought prior to insulin administration.


Hypoglycaemia means low blood sugar and can be life-threatening. It can occur if insulin dosage is too high, or if the cat has not eaten. It occurs at peak insulin activity, usually five hours after administration. Signs commonly include lethargy, weakness, shaking, head tilt and signs of disorientation, which may progress to convulsions and coma. If concerned, offer the cat its normal food or syringe feed a small amount of sugar solution and seek veterinary advice.

Should you wish to discuss any of these issues in more detail, please consult your veterinary surgeon.