Diabetic ketoacidosis (DKA), a serious complication of decompensated diabetes mellitus (DM), is associated with considerable morbidity and mortality in veterinary patients as it results in major fluid, electrolyte, and acid-base disturbances and usually occurs with a comorbid process. The pathophysiology of DKA involves a relative or absolute insulin deficiency combined with an increase in circulating counter-regulatory hormones (CRH; such as glucagon, cortisol, epinephrine, and growth hormone) typically arising secondary to a concurrent disease process. The increased CRH:insulin ratio eventually results in hyperglycemia and ketonemia, with subsequent glucosuria and ketonuria. Treatment of DKA is aimed at restoring intravascular volume, reducing hyperglycemia while reversing ketonuria, correcting acid-base and electrolyte imbalances, and managing any concurrent disease processes. Prognosis of DKA is variable in that it is largely dependent on the underlying comorbidity.