Dog: Diabetes Mellitus

General information

Diabetes mellitus is a disorder caused by an insufficiency or absence of insulin. Insulin is a hormone which is produced by the pancreas. It maintains the blood glucose or sugar at a constant, appropriate level by allowing the body’s cells to absorb and utilize glucose. Glucose comes from the diet and provides energy to the cells. It is delivered to the cells via the blood supply. Without insulin, glucose cannot be used by the cells, the blood glucose level increases (hyperglycemia) and the body believes it is starving. Because of this, the body begins to make more glucose by breaking down body fat, stored starches and protein to supply calories to the cells. However, the processing of fat for energy leads to the production of ketones rather than glucose. An increase in ketones in the blood can result in ketoacidosis which is a life-threatening complication of diabetes.

The pancreas is a pale pink glandular organ which is found under the stomach and along the initial part of the small intestine or duodenum. The pancreas has two main functions. As stated before, it produces and secretes insulin for sugar metabolism. A second function is secretion of enzymes which aid in the digestion of food. A dysfunction in this area can result in pancreatitis or pancreatic insufficiency.

Abb. GSHBWQYV: Schematic illustration of the canine gastrointestinal system showing the location of the pancreas.


The cause of diabetes in dogs can be difficult to pinpoint but include:

  • Genetic susceptibility-Keeshond, Miniature Pinscher, Poodle and Miniature Schnauzer
  • Chronic pancreatitis causing pancreatic destruction
  • Immune-mediated disease causing pancreatic destruction
  • Obesity
  • Infection
  • Drugs such as corticosteroids
  • Diseases such as Cushing’s Disease
  • Progesterone-unspayed females or dogs taking progesterone-related medications are more prone to uncontrolled diabetes

Cardinal symptom

  • Increased thirst
  • Increased urination


Increased thirst and increased urination are two classic symptoms of diabetes mellitus. Glucosuria or glucose in the urine occurs when the increased level of glucose in the blood spills over into the urine. Because glucose carries a lot of extra water, glucosuria leads to excess urine production and dehydration. Dogs compensate by drinking excessive amounts of water. Other typical clinical signs include an increase in appetite, weight loss and lethargy due to the cell’s inability to absorb and utilize the blood glucose. If left untreated, ketoacidosis can occur resulting in lack of appetite, vomiting, diarrhea and neurologic signs.

Cataracts (opacities in the ocular lens) are common in dogs with diabetes. These result when increased blood glucose is deposited into the lens. The glucose then draws water into the lens causing the cloudiness. Dogs with diabetes are more prone to infections. Cystitis or urinary tract infections are more common in diabetic female dogs.

Abb. GFZ2Q6VW: Cataracts.
This is a photograph of a dog with obvious cataracts due to diabetes.


Diabetes mellitus is diagnosed by clinical signs along with an increased level of glucose in the blood and in the urine. The laboratory tests used are a complete blood count (CBC), serum biochemistry and urinalysis.


The goal in the treatment of diabetes is to maintain a dog’s normal glucose level (regulated diabetes) which will reduce the clinical signs. This is accomplished by providing insulin replacement, a balanced diet and consistent exercise. Dogs which present with signs of ketoacidosis should receive emergency treatment to prevent shock and death.

Insulin replacement

Almost all diabetic dogs will need insulin replacement. There are several different types of insulin characterized by their source and duration of action. Insulin for dogs can be derived from pork or beef or produced in a human recombinant form. It can be short-acting, intermediate-acting or long-acting. Some insulins are available from a human pharmacy and others are available through your veterinarian.

Initially, your dog will be hospitalized. The amount and frequency of insulin will be determined based on your dog’s signs and glucose levels. Most dogs will require injections given twelve hours apart following a meal. Once your dog has been regulated in the veterinary clinic, you will be trained to give the injections at home. The injections are given in the subcutaneous tissue underneath the skin. Most dogs tolerate these injections well. Small, specialized needles and syringes are used to administer the exact amount of insulin. Care must be taken when handling insulin. It should be kept refrigerated and mixed gently by rolling the bottle, never shaken.

Your veterinarian may recommend monitoring your dog’s blood glucose or urine glucose at home. These methods have their advantages and disadvantages.

Frequent recheck examinations and blood glucose measurements will be needed to monitor your dog’s progress. A glucose curve will be performed by taking multiple blood samples throughout the day and testing the glucose levels to determine if the type, amount and frequency of insulin is correct. Fructosamine levels can be measured to reveal the average blood glucose level for the previous two weeks. This will indicate whether the diabetes is being controlled.


Most veterinarians recommend a specially formulated, prescription diet for the diabetic dog. Some dogs will respond well to high protein, low carbohydrate diets whereas others respond to high fiber diets. Because insulin requirements change depending on the amount and type of food eaten, a consistent high quality diet that your dog will eat is important. Table food, soft-moist diets and sugary treats must be avoided. Strict feeding schedules may be necessary.


Exercise not only causes the blood glucose to decrease but helps your dog maintain a healthy weight. Dogs can be taken for walks or encouraged to play. To help regulate the diabetic dog, it is important to keep the activity level the same from day to day.


There is no cure for diabetes mellitus. Long-term management and commitment to a treatment regimen are necessary. Left untreated or unregulated, diabetes can have life-threatening consequences such as ketoacidosis, kidney or liver disease. However, with vigilance to insulin replacement, diet and exercise, diabetes is a treatable condition.


Preventing your dog from becoming overweight can help to prevent diabetes mellitus.


The most serious side effect of too much insulin is hypoglycemia or low blood glucose. Hypoglycemia can be a life-threatening condition. Signs of hypoglycemia include weakness, wobbliness, shivering, disorientation and seizures. If this occurs, encourage your dog to eat. If unable to eat, rub Caro syrup or honey onto the gums. Call your veterinarian immediately.

Update version: 4/24/2014, © Copyright by
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