Diabetes Mellitus in Dogs and Cats

Diabetes mellitus results when insulin production is reduced or abolished (secretory defect) or when insulin action at target tissues is impaired (insulin resistance).The metabolic defects of diabetes primarily include hyperglycemia and hyperlipidemia, although electrolyte abnormalities, dehydration,ketosis, and metabolic acidosis may develop with severe insulin deficiency when treatment is delayed.

Prompt and effective treatment of diabetes is necessary to prevent catastrophic metabolic complications, but treatment of diabetes is associated with complications as well, some of which can be life-threatening.

Types of Complications

The complications associated with diabetes mellitus fall into two general categories: those that arise from untreated diabetes and those that develop during treatment for diabetes. The emergency management of complicated diabetes has been reviewed in detail and is not addressed here.

This article focuses on the causes and treatments of complications that develop in dogs and cats during treatment of diabetes mellitus. Complications associated with diabetes treatment may be classified as acute or chronic. Acute complications are those directly related to insulin administration and can occur in new and established diabetics. Chronic complications occur when diabetes therapy is in the maintenance phase and usually result from poorly controlled diabetes.

Acute complications

Hypoglycemia: Insulin-induced hypoglycemia is a severe and potentially life-threatening complication of diabetes treatment. Under some circumstances, insulin therapy can precipitate hypoglycemia as well as exacerbate or promote hypophosphatemia, hypokalemia, and hypovolemia. Hypoglycemia in established diabetics may occur after pharmacologic insulin doses or accidental insulin overdose. In any circumstance, unrecognized or untreated hypoglycemia.

Complications of Treatment of Diabetes Mellitus can cause significant morbidity and may be fatal in some patients.2 In some poorly regulated diabetic patients, chronic subclinical hypoglycemia or episodic bouts of clinical hypoglycemia may occur. The latter situations largely reflect problems with diabetic management that require reevaluation of the insulin therapy protocol.


In diabetic dogs and cats, hypophosphatemia usually develops after insulin treatment has begun and is caused by rapid insulin-mediated cellular uptake of phosphorus. Severe hypophosphatemia (phosphorous levels < 1.0 mg/dl) causes hemolysis, which can be life-threatening.

Decreased serum phosphorus impairs adenosine triphosphate generation and reduces 2,3-diphosphoglycerate concentrations in red cells, which leads to red cell fragility and reduced oxygen delivery. Massive hemolysis can develop when serum phosphate falls below the critical level needed to maintain red cell integrity.

Hypophosphatemia may also cause varying degrees of rhabdomyolysis, ileus, and encephalopathy.

Hypokalemia and hypomagnesemia:

These may be noted at diagnosis or develop during the treatment of ketoacidosis and other complicated forms of diabetes. Total-body potassium and magnesium may be depleted in diabetics because of reduced dietary intake and increased renal and gastrointestinal losses.

During diabetes treatment, fluid diuresis promotes renal loss of potassium and magnesium, and insulin treatment can precipitate or exacerbate hypokalemia and hypomagnesemia by promoting cellular water and solute uptake.