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Diabetes Mellitus in Dogs

Diabetes mellitus is a disease state by which the body suffers from either an absolute shortage of insulin (Type I or insulin dependent), or from an incorrect response from the cells to the insulin that is being produced, a condition termed insulin resistance (Type II or insulin resistant). Both of these conditions will prevent the muscles and organs from converting glucose to energy and will result in excessive amounts of glucose in the blood, which is also referred to as hyperglycemia.

Diabetes is a disorder of carbohydrate, protein, and fat metabolism caused by an absolute or relative insulin deficiency. Metabolism refers to how the body digests and uses food for growth and energy; this process is largely dependent on a sufficient amount of insulin in the body.

Insulin is a hormone that is produced in the pancreas and released into the cells in response to the digestive conversion of carbohydrates and protein into glucose in the bloodstream. Much of the food that is ingested is broken down into glucose, a type of sugar in the blood and one of the body's main sources of energy. Appropriate insulin function will trigger the liver and muscles to take up glucose from the blood cells, converting it to energy.

Diabetes, a common condition for humans, is also relatively common in domestic animals like dogs. In Type I diabetes, the pancreas has stopped producing insulin entirely. Affected dogs are dependent on daily insulin injections for maintaining blood sugar balance (insulin dependent diabetes mellitus – IDDM). This is the most commonly diagnosed type of diabetes in dogs.

In Type 2 diabetes, the pancreas can still produce insulin, but the body cannot adequately respond to it. While the disease process is not exactly the same in dogs as it is in people, dogs can develop insulin resistant diabetes (IRD.)

An affected dog will be hungry a lot of the time. Since glucose is not making it to the brain, glucose levels in the brain are too low for the brain to register that it is receiving food. Because insulin is not giving the muscles and organs the signal to convert glucose to energy, the excess glucose in the blood will be carried out of the body in urine instead of being used for energy and there will be a concurrent lack of energy. The glucose ends up in the urine, where it interferes with normal urine concentration and leads to an increase in urination. The pet becomes dehydrated as a result of the abnormal water loss, so there is also increased thirst. The liver is adversely affected by this condition, as are the eyes and kidneys. Affected pets are also at increased risk for systemic infections, dental disease, and cataracts.

IDDM diabetes can occur at any age. IRD diabetes is seen more frequently in older, obese, and desexed dogs, though it can also occur at any age. 

Symptoms and Types of Diabetes in Dogs

Early signs

  • Excessive urination
  • Excessive thirst
  • Hunger
  • Weight loss even with normal appetite
  • Elevated blood glucose
  • Glucose in the urine

Later signs

  • Anorexia – complete loss of appetite
  • Lethargy and depression
  • Vomiting
  • Cataracts
  • Worsening weight loss
  • Recurrent infections

Development of Ketoacidosis – A life threatening complication of unregulated diabetes, diabetic ketoacidosis (DKA) is a metabolic acidosis caused by the breakdown in the liver of fat to ketones in response to starvation.

  • Depression
  • Vomiting
  • Collapse
  • Coma
  • Death

Causes of Diabetes in Dogs

There are several possible causes for diabetes mellitus. Genetic predisposition is one likely cause, as some breeds seem to be predisposed to diabetes, and dogs that have diabetes may also have affected relatives.

Some medical conditions predispose a dog to developing diabetes. The conditions most commonly associated with diabetes are Cushings, pancreatitis and obesity.

The following breeds are at a higher risk:

Diagnosis of Diabetes in Dogs

Your veterinarian will take a detailed medical history from you of your dog's health leading up to the onset of symptoms and details of the exact symptoms. Standard tests will include a complete blood count, chemical profile, and urinalysis. These tests should be sufficient for diagnosis and initial treatment.

Typically, with diabetes, an unusually high concentration of glucose will be found in the blood and urine. Abnormally high levels of liver enzymes and electrolytes imbalances are also common. In severe cases, urine test results may also show evidence of abnormally high levels of ketone bodies — water-soluble compounds produced as a by-product of fatty acid metabolism in the liver and kidney. A numbers of other abnormalities may also be found.

Radiographic studies, including x-rays and ultrasonography, can be helpful for the diagnosis of concurrent diseases and complications due to diabetes. Abdominal X-rays and ultrasound will help to determine the presence of kidney stones and/or inflammation of the pancreas and liver as well as other associated abnormalities. In the case of liver disease, should it appear suspect, your veterinarian may decide to take a sample of liver tissue for further diagnostic evaluation.

Treatment and Care for Diabetic Dogs

Your veterinarian will prescribe a course of treatment for your dog to get his or her blood glucose in a normal range. This almost always requires twice daily insulin injections combined with diet and exercise. Management of newly diagnosed diabetes can be challenging at first as it often requires regular blood glucose checks and adjustments, but with adequate attention and support many owners quickly adjust to the new routine.

Obesity is one of the major risk factors for diabetes and this condition can make management of diabetes difficult, but obesity can only be brought under control slowly and with great care. The target weight may be reached in 2-4 months, but your veterinarian will need to suggest a practical timeline that is appropriate for your dog. If your dog has actually lost weight due to diabetes, you will need to work with your veterinarian on a plan to increase your dog's weight to normal levels.

Do not change your dog food suddenly and without first discussing it with your veterinarian. Your dog will need a well-thought out and strictly enforced diet plan. Your veterinarian can help you to design a plan that is well suited to your dog's needs, with lifestyle changes to facilitate proper management of the diabetes.

Your veterinarian will make an individual treatment and management plan for your dog based on the dog's current disease status. Your veterinarian will also brief you on what to look for in case of either hypoglycemia (low levels of glucose) or hyperglycemia (high level of glucose), both of which can be seen in diabetic dogs. Keeping a daily and weekly chart of your dog's diet, glucose test results, daily insulin dose, and weekly body weight is highly recommended for following patterns and recognizing when your dog deviates from his or her regular pattern. There are various types of insulin available and a selection of the type that is appropriate to your dog will be made by your veterinarian.

If this is a serious issue, and there are no plans to breed, your veterinarian will recommend a hysterectomy for your female dog. This is to avoid the surge of hormones at the time of estrus, which can further complicate your dog's health. Unfortunately, this is not a disease that will be cured, but your dog's health can be kept stable and it can go on to live a fully enjoyable life. This will be dependent on your willingness to adhere to your doctor's dietary recommendations. If properly managed, diabetic patients can live a long and healthy life. The best preventive from complications is practicing careful maintenance.

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