Diabetes in Cats & dogs


Diabetes Mellitus is a medical condition where there is an excessive amount of glucose (sugar) in the blood. This is caused by a deficiency of the hormone insulin, which is secreted by the pancreas. Insulin helps the body use glucose as an energy source. Diabetes Mellitus is an uncommon disease in cats and is seen more frequently in overweight, middle aged to older cats, and is more common in males than females. Common clinical signs of diabetes are:

  • Increased drinking
  • Increased urination volume
  • Increased appetite
  • Weight loss

Clinical signs start to show as a result of high concentrations of glucose in the blood, and the inability of the body to use the glucose as an energy source.
A diagnosis of diabetes cannot be made on a single blood and urine sample as other conditions, such as stress, can cause a rise in glucose levels. Another blood test called a fructosamine test, can be performed which measures the average of blood glucose levels.

How is Diabetes Mellitus treated?

Diabetes Mellitus is a long term treatable condition usually managed with giving insulin injections twice a day. Regular veterinary check-ups to test blood glucose levels are then required to make sure the insulin dose is effective.


There are two forms of diabetes in dogs; diabetes insipidus and diabetes mellitus. Diabetes insipidus is sometimes called ‘drinking diabetes’ and diabetes mellitus is also known as ‘sugar diabetes’. Diabetes insipidus is a very rare disorder that results in failure to regulate body water content. Diabetes mellitus is more common in dogs, and is frequently diagnosed in dogs five years of age or older. This is also known as adult-onset diabetes. There is a congenital form that occurs in puppies called juvenile diabetes, but this is rare in dogs.

What is Diabetes Mellitus?

Diabetes mellitus is a disease of the pancreas. This is a small, but vital organ located near the stomach. It has two significant populations of cells. One group of cells produces the enzymes necessary for proper digestion. The other group, called beta-cells, produce the hormone insulin. Diabetes mellitus is a failure of the pancreatic beta cells to regulate blood sugar. Most dogs with diabetes mellitus will require daily insulin injections to regulate their blood glucose.

Type I or Insulin Dependent Diabetes Mellitus results from total or near-complete destruction of the beta-cells. This is the most common type of diabetes in dogs. As the name implies, dogs with this type of diabetes require injections to stabilise blood glucose levels.

Type II or Non-Insulin Dependent Diabetes Mellitus is different because some insulin-producing cells remain. However, the amount produced is insufficient, there is a delayed response to secreting it, or the tissues of the dog’s body are relatively resistant to it. Type II diabetes most commonly occurs in older obese dogs and is the most common form in both people and cats.

Insulin is important because it is the hormone responsible for how the body regulates and manages its fuel (sugars and fats) and its protein building blocks (amino acids). Insulin promotes the uptake, storage and use of the sugars, fats and amino acids within the body. Insulin controls glucose leaving the blood stream and passing into the cells. Glucose is a vital substance that provides much of the energy needed for life, and it must work inside the cells. Without an adequate amount of insulin, glucose is unable to get into the cells. It accumulates in the blood, setting in motion a series of events that can ultimately prove fatal.

When insulin is deficient, the cells become starved for a source of energy and the body starts breaking down stores of fat and protein to use as alternative energy sources. As a consequence the dog eats more, thus we have weight loss in a dog with a ravenous appetite. The body tries to eliminate the excess glucose by excreting it in the urine. However, glucose attracts water resulting in the production of a large amount of urine. To avoid dehydration the dog drinks more and more water, thus we have the four classic signs of diabetes:

  • Increased water consumption
  • Increased urination
  • Increased appetite
  • Weight loss

How is Diabetes diagnosed?

The diagnosis of diabetes mellitus is based on three criteria; the clinical signs identified above, the presence of a persistently high level of glucose in the blood stream, and the presence of glucose in the urine.

How is Diabetes treated?

For the diabetic dog one reality exists, blood glucose cannot be normalised without treatment. Although a dog can go a day or so without treatment and not have a crisis, treatment should be looked upon as part of the dog’s daily routine. Treatment almost always requires some dietary changes and the administration of insulin.

  • Diet – diets high in fibre are preferred in dogs because they are generally lower in sugar and slower to be digested. This means that the dog does not have to process a large amount of sugar at one time. Additionally, the fibre may stimulate insulin secretion in type II diabetes.
  • Insulin injections – This involves the injection of insulin once or twice a day. It is administered subcutaneously (under the skin), at the scruff of the neck. These can be given at home, usually at the same times daily. Individual dogs respond differently to insulin, and the dose may need to be adjusted based on blood glucose profiles, clinical response & urine glucose monitoring.
  • Monitoring – careful monitoring of appetite, weight, water consumption and urine output is vital.
  • Testing – regular urine testing can be done at home. Blood glucose levels will also need regular testing by the vet.

Upon the diagnosis of diabetes in your pet, your vet will work with you to establish a management plan you are comfortable with. It will involve regular testing of urine and giving injections. These can mostly be performed at home by the owner after adequate training from your vet. It is important to regularly monitor your dog & work closely with your veterinarian.
If properly managed, a diabetic dog can live for many happy years.