Diabetic ketoacidosis (DKA) is a potentially life-threatening complication of diabetes mellitus. Signs and symptoms may include vomiting, abdominal pain, deep gasping breathing, increased urination, weakness, confusion and occasionally loss of consciousness. A person's breath may develop a specific "fruity" smell. Onset of symptoms is usually rapid. People without a previous diagnosis of diabetes may develop DKA as the first obvious symptom.

DKA happens most often in those with type 1 diabetes but can also occur in those with other types of diabetes under certain circumstances. Triggers may include infection, not taking insulin correctly, stroke and certain medications such as steroids. DKA results from a shortage of insulin; in response, the body switches to burning fatty acids, which produces acidic ketone bodies. DKA is typically diagnosed when testing finds high blood sugar, low blood pH and ketoacids in either the blood or urine.

The primary treatment of DKA is with intravenous fluids and insulin. Depending on the severity, insulin may be given intravenously or by injection under the skin. Usually, potassium is also needed to prevent the development of low blood potassium. Throughout treatment, blood sugar and potassium levels should be regularly checked. Underlying causes for the DKA should be identified. In those with severely low blood pH who are critically ill, sodium bicarbonate may be given; however, its use is of unclear benefit and typically not recommended.

Rates of DKA vary around the world. Each year, about 4% of type 1 diabetics in the United Kingdom develop DKA, versus 25% of type 1 diabetics in Malaysia. DKA was first described in 1886, and until the introduction of insulin therapy in the 1920s, it was almost universally fatal. With adequate and timely treatment, the risk of death is between <1% and 5%.