Diabetes Mellitus in Domestic Animals

Diabetes Mellitus is a condition in which there is a deficiency of the hormone insulin or an insensitivity to it. Insulin is responsible for controlling blood concentrations of the body’s main fuel, glucose.

In a diabetic animal there is insufficient insulin to switch off glucose production by the liver or to efficiently store excess glucose derived from energy giving foods. This means that the blood concentration of glucose rises and eventually leaks into the urine. This loss of glucose in urine takes water with it by a process called osmosis and causes larger volumes of urine to be produced than normal, leading to increased water consumption. The principal clinical signs of an animal with diabetes mellitus are therefore polyuria (excessive urination) and polydipsia (excessive water consumption). In addition, diabetic animals tend to lose weight because they breakdown stores of fat and protein (muscle) to make glucose and ketones (an alternative fuel) in the liver. Other clinical signs may include: cataracts, polyphagia (increased appetite), exercise intolerance, recurrent infections, fits, coma and death.



Oral hypoglycaemics

Oral hypoglycaemics are tablets used in the treatment of human diabetes mellitus which can lower blood glucose in some cases. In general, they are not useful for the treatment of diabetes in dogs but may be useful in a small proportion of diabetic cats.


Insulin, administered by injection, is the treatment of choice for diabetes mellitus in animals.


Diet can be a very useful means to control Diabetes, and in many cases can reverse the signs of diabetes, notably in type-2 diabetes. Restriction of carbohydrate intake, particularly high glycaemic index carbs, helps to control sugar levels in the blood. It must be noted that diet change alone is not always the definitive solution, so careful monitoring of the patient’s glucose levels and health is important.

To keep diet constant from day to day it is best to use commercially produced rather than home-made diets. Certain prescription or veterinary diets can be a useful adjunct to insulin therapy such as Hill’s w/d or r/d.


Unfortunately, there is no standard dose for insulin which can be applied to all animals. Each diabetic animal has to have its dose tailored to its individual needs which is done over a stabilization period, either at the vet or at home. After such a period, maintenance insulin doses should remain relatively constant. All the other factors which affect blood glucose concentration must be kept constant from day to day, including the composition, volume and timing of meals and the amount of exercise the animal gets.

The insulin treatment of cats is similar to that of dogs but requires at least twice daily injections of insulin because cats metabolize insulin much more rapidly than dogs.

Somogyi overswing is an insulin induced hyperglycaemia (high blood sugar). Excessive insulin dose lowers blood glucose too far and the body responds to this potentially life threatening situation by raising the blood glucose, often to very high levels. This can be mis-interpreted and the insulin dose increased, which will, in fact, only make matters worse. The possibility of inducing Somogyi overswing can be reduced by measuring urine glucose 3 times a day or by serial blood glucose tests.


Problem cases


In diabetic animals treated with insulin there is some risk that hypoglycaemia may occur. It is most likely to happen if the animal is accidentally over-dosed with insulin, over-exercised or fails to eat its morning meal. The first noticeable clinical sign is hunger followed by lethargy and sleepiness. If untreated, stumbling and staggering ensue followed progressively by twitching, convulsions, coma and death. Treatment is by offering food, particularly glucose containing foods such as biscuits, or by rubbing oral glucose gels or dissolved powders on the gums. These are absorbed very rapidly.


Ketoacidotic animals are usually collapsed, dehydrated and smell of ketones (like nail varnish remover). These dogs require more intensive therapy than normal diabetic dogs and this should include intravenous fluid and special soluble insulin therapy. This is an intensive care situation and the animal must be taken to a veterinary care facility.

Insulin Resistance

Some cases are resistant to certain insulin types and need higher doses or different forms of insulin.



While there’s no cure for diabetes, proper care can help your pet live a happy, healthy, active life. The more you know about diabetes, the better you’ll be able to work with your veterinarian to successfully manage your pet’s health.