The mortality rate of diabetic hyperosmolar coma is around 40%. Hyperosmolar coma is a common acute complication of diabetes mellitus, mostly occurring in elderly patients with no previous history of diabetes mellitus, and can be precipitated by obvious triggers, such as infection, acute gastroenteritis, cardiovascular disease, and heavy glucose use. Patients with hyperosmolar coma mostly have atypical diabetic symptoms, mainly mental and neurological symptoms caused by fluid loss, such as drowsiness, hallucinations, disorientation, epileptic-like convulsions, etc., or they can go directly into coma. The causes of hyperosmolar coma are related to poor cerebrovascular function, extreme hyperglycemia, and severe dehydration in elderly patients, resulting in elevated plasma osmolarity and dehydration of brain cells, which leads to prominent neurological symptoms. The mortality rate of hyperosmolar coma is high, at around 40%. Once diagnosed, it needs to be treated aggressively with immediate measures such as rapid infusion, volume expansion, correction of hyperosmolarity, reduction of blood glucose, and symptomatic management.