Diabetic ketoacidosis is an emergency medical condition that can be life-threatening if not treated properly. Diabetic ketoacidosis occurs most often in patients with type 1 diabetes (formerly called insulin-dependent diabetes mellitus); however, its occurrence in patients with type 2 diabetes (formerly called noninsulin-dependent diabetes mellitus) is not as rare as was once thought. This article reviews data about precipitating events, pathogenesis, carbohydrate, lipid and ketone, water and electrolyte metabolism in this hyperglycemic crisis. The review discusses diagnostic procedures, laboratory evaluation, differential diagnosis and treatment: replacement of fluid and electrolytes, low-dose insulin therapy and recommendations for use of bicarbonate. A discussion of complications management of diabetic ketoacidosis (hypoglycemia, hypokalemia, cerebral edema, hyperchloremic metabolic acidosis, pulmonary edema, adult respiratory distress syndrome), mortality rate and prevention are included in this review.