What is diabetes?

Diabetes is a metabolic disease of middle and old aged dogs, whose symptoms are caused by high blood sugar, due to lack of the hormone insulin. Obesity is the main predisposing factor.

After a meal blood glucose (sugar) rises. Insulin stimulates the body to store excess glucose as starch in the liver. Lack of insulin results in the blood glucose level being too high, which causes glucose to leak into the urine. Glucose draws extra water into the urine, making the dog produce more urine and be thirstier.

High blood sugar can also cause cataracts (cloudiness of the lens in the eye). In diabetic dogs metabolism is altered so that the body has to break down fat and muscle tissue to provide it with energy. This causes weight loss.

Altered metabolism can also lead to the production of damaging acids called ketones, which in large amounts cause illness or even death.


The major signs are:

  1. Increased thirst
  2. Increased urination
  3. Increased hunger
  4. Weight loss
  5. Vomiting
  6. Lethargy
  7. Blindness


Diabetes is diagnosed by a combination of veterinary examination, blood and urine tests. Dogs with diabetes will have high blood glucose and glucose in their urine. They may also have other biochemical abnormalities, such as signs of liver damage. If there is any doubt a test for fructosamine can be done, which indicates the average blood glucose over the previous 1-2 weeks.

Some dogs will be very ill when diagnosed, with a life threatening condition called diabetic ketoacidosis. The blood and urine glucose levels and blood and urine ketones are all very high. This condition requires intensive care.

In dogs diabetes is always treated with insulin injections, usually given twice a day, for life. These injections are given by the dog’s owners. Owners are trained by a veterinary nurse on exactly how to store, handle and use the insulin and how to give injections. Normally the dog must eat before insulin is injected. If the dog does not eat, owners should contact the surgery for advice.

Other factors that will help to control diabetes include:

  • Controlled weight loss if the dog is overweight – ideally under the supervision of a veterinary nurse.
  • Feeding a high fibre diet that releases glucose slowly. Special prescription diets are available.
  • Ensuring that the dog has the same amount of exercise at the same times every day, so that glucose use is the same every day.
  • Spaying entire female dogs. The hormone changes that occur in entire bitches prevent good control of diabetes. In diabetic dogs hormone injections are not a viable alternative to spaying.
  • Treating any other disease processes the dog may have.

On average diabetic dogs treated with insulin live for about 2 years after diagnosis.


Monitoring diabetes control is essential. The blood sugar level should be reduced but should not be too low. Usually the dog will be admitted to the surgery for 12-24 hours for a glucose curve (measuring blood glucose every 1-2 hours and plotting the results on a graph), either on the day treatment starts or soon after, to see how well the insulin is controlling blood glucose. It may take some time before the right dose is reached. Ideally a glucose curve will be done to monitor each dose change and then every 3-6 months after the correct dose is reached or if control seems to have been lost.

Other important ways of monitoring control include:

  • Recording daily food and water intake (with good control thirst and hunger should be reduced).
  • Monitoring how well the dog is in itself Doing glucose curves at home.
  • Glucometers, to measure blood glucose, can be bought or hired, and samples can be taken with a special pin-prick.
  • Blood fructosamine measurement.


Problems are, unfortunately, common, including:

  • Hypoglycaemia (low blood sugar) – where the dog becomes weak and wobbly. This emergency condition can be treated with sugar, jam or honey given by mouth.
  • Diabetic ketoacidosis – dogs become really ill and may be vomiting. This is an emergency condition.
  • Incorrect storage or handling of insulin. Incorrect dosing or injecting.
  • Diabetic dogs are more likely than normal to develop urinary and other infections, such as periodontal disease.
  • Infections or inflammation make the body less responsive to insulin.  Diabetic cataracts may appear even if diabetes control is good.
  • Other diseases of middle or old age, such as Cushing’s disease, may interfere with control of diabetes.
  • Occasionally dogs become resistant to the type of insulin being used.
  • Rarely, if the blood sugar drops too far, the body may react by massively increasing blood sugar.


Diabetes is a complex metabolic disease, with symptoms caused by high blood glucose, which requires lifelong treatment with insulin injections.