Table 1.

Causes of hypoglycemia in the dog broadly divided by the presence or absence of an underlying disease resulting in hypoglycemia (1,6).

Physiological causes of hypoglycemia	Chief mechanism or mechanisms
Extreme exercise (e.g., hunting dog hypoglycemia)	Excess glucose utilization and inadequate glycogen stores
Neonatal/juvenile or toy breed juvenile hypoglycemia	Inadequate glycogen stores, limited fat and muscle mass
Malnutrition/starvation	Inadequate intake and depletion of glycogen stores
Drug and toxin associated causes such as iatrogenic insulin overdose, xylitol toxicity, oral hypoglycemic agents (usually sulfonylureas), beta blockers	Excess glucose utilization due to hypersecretion of insulin and increased tissue sensitivity to insulin. Beta blockers via suspected interference of counter- regulatory mechanisms
Pathological causes of hypoglycemia
Severe hepatic disease such as hepatitis, cirrhosis, neoplasia, amyloidosis, hepatotoxins	Decreased hepatic gluconeogenesis
Congenital portosystemic shunt	Decreased hepatic gluconeogenesis
Hypoadrenocorticism	Decreased glucose production from lack of a counter-regulatory hormone (i.e., cortisol)
Hypopituitarism	Decreased glucose production from lack of a counter-regulatory hormone (i.e., growth hormone or adrenocorticotropic hormone)
Insulinoma	Excess glucose utilization due to hypersecretion of insulin
Islet cell hyperplasiaa	Excess glucose utilization due to hypersecretion of insulin
Extra-pancreatic tumors (e.g., hepatocellular carcinoma, hepatoma, leiomyosarcoma, leiomyoma)	Increased glucose utilization by the tumor but also due to secretion of insulin analogues
Chronic renal failure	Decreased hepatic gluconeogenesis
Pancreatitis	Unknown
Infection (e.g., sepsis, severe canine babesiosis)	Decreased hepatic glycogenesis and increased glucose utilization
Glycogen storage disease	Deficiency of enzymes required for glycogen conversion
Artifactual/spurious	Laboratory error from improper sample handling or submission, use of a human glucometer, leukemia/polycythemia vera

^aReported as a rare cause of hypoglycemia in humans.

This pancreatic pathology has been documented in dogs but without hyperinsulinemic hypoglycemia syndrome.