Diabetes mellitus is a common endocrinopathy in middle-aged and older dogs and is a complex disorder of carbohydrate, protein, and lipid metabolism. This disorder, which is the result of a relative or absolute insulin deficiency or of peripheral cell insensitivity to insulin, is characterized by high blood glucose concentrations such that the renal threshold is exceeded. As a result, glucose is excreted in the urine.
The osmotic action of glucose leads to polyuria and, through response to loss of fluid, to polydipsia. In addition, metabolism is impaired so that the general condition of the animal deteriorates, ultimately leading to death if untreated.
Insulin is synthesized in and released from beta cells in the pancreatic islets. Insulin assists with cellular uptake of glucose from the bloodstream, thus exerting a glucose-lowering effect. Within cells, insulin promotes anabolism (such as synthesis of glycogen, fatty acids, and proteins) and counters catabolic events (reduces gluconeogenesis and inhibits fat and glycogen breakdown).
Whereas insulin lowers blood glucose, there are opposing hormones (glucagon, cortisol, progesterone, adrenaline, thyroid hormone, and growth hormone) that act to increase blood glucose. It is important to consider these counter-regulatory hormones, because changes in their blood concentrations will interfere with insulin actions. Changes in these hormones can occur in natural physiological conditions, in disease states, or as a consequence of drug administration.
In the absence of sufficient insulin, dogs with diabetes will switch from glucose to fat metabolism for cellular energy. While this is initially beneficial, fat metabolism in unrecognized or untreated diabetes typically progresses to ketoacidosis and ultimately to death.
Diabetes mellitus is not related to diabetes insipidus, an uncommon condition that occurs when the kidneys are unable to regulate fluids in the body. Diabetes insipidus is characterized by a deficiency or inadequate response to a hormone called vasopressin.
Estimates of the prevalence of diabetes mellitus in dogs is up to 23.6 canine cases per 10,000.1
Certain breeds appear to be at greater risk for developing canine diabetes:
- Cocker Spaniels
- Dachshunds
- Doberman Pinschers
- German Shepherds
- Golden Retrievers
- Labrador Retrievers
- Pomeranians
- Terriers
- Toy Poodles
- Miniature Schnauzers
- Keeshonds
- Samoyeds
Diabetes typically occurs when dogs are between 4 to 14 years of age. Unspayed female dogs are twice as likely as male dogs to suffer from diabetes.
1 Banfield State of Pet Health 2016 Report. p 12-13.
The prognosis for diabetes mellitus depends mainly on the cause of it, early diagnosis and adequate therapy. In general, the prognosis is very good, provided that diagnosis is made at an early stage and therapy is administered properly.
Most forms of diabetes can be successfully managed with insulin, the cornerstone of successful management, but dietary adjustments and a regular lifestyle are also important.
Open communication between client and veterinarian is also extremely important. Your encouragement will largely influence the dog owner’s motivation and compliance with therapy. Clients need to fully understand the disease to help achieve and maintain good diabetic stability and be highly motivated and committed to the management of their dog.
The clinical staff should also understand the basics of diabetes and its management. They have an important role in providing detailed client education, instruction, and encouragement.
Several classification systems have been used to describe diabetes mellitus. A human classification system revised in 1997 divides the disease into three types: Type 1 (previously insulin-dependent or juvenile-onset diabetes mellitus), Type 2 (previously non–insulin-dependent or adult-onset diabetes mellitus), and other specific types of diabetes mellitus (previously secondary or Type 3 diabetes mellitus).
Diabetes in dogs most closely resembles Type 1 diabetes. Dogs with the insulin-dependent form of the disease require daily insulin injections to control disease signs and delay the multisystemic disorders associated with the diabetic disease process. The use of oral hypoglycemic drugs is not recommended in dogs with diabetes as they typically require insulin production, which dogs lack.
Untreated dogs commonly display weight loss despite maintaining a good or excessive appetite, polydipsia, and polyuria. They may experience dehydration and metabolic and electrolyte abnormalities if severe ketoacidosis develops. Untreated or improperly managed dogs with diabetes suffer a decreased quality of life, and most die without appropriate therapy and monitoring.
Glucose toxicity occurs when insulin secretion is reduced by prolonged hyperglycemia. Prolonged hyperglycemia can occur due to a number of causes. The prolonged and high-dose therapeutic use of glucocorticosteroids can induce diabetes mellitus. The use of exogenous progestogens can lead to growth hormone excess. Progestogens also have an affinity for glucocorticosteroid receptors.
If the insulin dose is too high, clinical signs of hypoglycemia may be observed. Hypoglycemia may also be triggered by events causing a relative insulin overdose:
• Loss of appetite
• Vomiting
• Excessive Exercise
The clinical signs of hypoglycemia, in increasing order of severity, are:
• Weakness and appetite loss
• Hunger
• Restlessness
• Shivering
• Ataxia
• Disorientation
• Convulsions and coma
- Immediate oral administration of glucose solution or corn syrup (1 g per kg body weight). Animals that are collapsed should not have large volumes of fluid forced into their mouths as this may result in aspiration pneumonia. Here it is preferable to rub a small amount of the glucose solution or corn syrup onto the animal’s gums or under its tongue.
- Owners of pets with diabetes should always have a source of glucose readily available. Following the successful emergency administration of oral glucose, small amounts of food should be offered at intervals of 1–2 hours until the effects of the insulin overdose have been counteracted.
- If the insulin dose is too high, it should be reduced, eg, by at least 10-50%. A follow up visit should be scheduled 1 week after dosage reduction to evaluation response to new dose.
2 Tennant B, ed. BSAVA Small Animal Formulary. 4th ed. Gloucestershire, UK: British Small Animal Veterinary Association; 2002.
Because dogs are more than just pets – they’re family
We help veterinary and pet owners give back to the animals that bring them joy and companionship.
