Diabetic ketoacidosis (DKA) is a life-threatening complication of type 1 and type 2 diabetes resulting from an absolute or relative insulin deficiency. It can occur in patients of all ages and can be the initial presentation of diabetes, especially in young children. Polyuria and polydipsia are the most common symptoms, followed by nausea, vomiting, abdominal pain, weight loss, severe fatigue, dyspnea, and preceding febrile illness. Traditionally, DKA has been diagnosed by the triad of hyperglycemia (blood glucose greater than 250 mg/dL), metabolic acidosis (pH less than 7.3, serum bicarbonate less than 18 mEq/L, anion gap greater than 10 mEq/L), and elevated serum (preferred) or urine ketones. However, hyperglycemia has been de-emphasized in recent guidelines because of the increasing incidence of euglycemic DKA. The use of sodium-glucose cotransporter-2 inhibitors modestly increases the risk of DKA and euglycemic DKA. Electrolytes, phosphate, blood urea nitrogen, creatinine, urinalysis, complete blood cell count with differential, A1C, and electrocardiography should be evaluated for all patients diagnosed with DKA to identify causes and complications of DKA. Amylase, lipase, hepatic transaminase levels, troponin, creatine kinase, blood and urine cultures, and chest radiography are additional tests to consider. Treatment involves fluid and electrolyte replacement, insulin, treatment of precipitating causes, and close monitoring to adjust therapy and identify complications. Prevention strategies include identifying diabetes before DKA develops, educating patients to manage high-risk situations, and ensuring uninterrupted access to therapies for diabetes.