Diabetic ketoacidosis is a common life-threatening complication, which usually occurs in patients with type 1 diabetes, but it may also occur in those with type 2 diabetes during severe concurrent illness, such as sepsis, myocardial infarction or corticosteroid treatment. This article provides an overview of the diagnosis, pathophysiology and management of diabetic ketoacidosis. The differential diagnosis and treatment of hyperosmolar non-ketotic coma is also discussed, as is the nurse’s role in promoting and providing health education to patients with diabetic ketoacidosis.