The main acute complications of diabetes are diabetic ketoacidosis, hyperglycemic hyperosmolar syndrome, and hypoglycemia. Diabetic ketoacidosis is the most common acute complication of diabetes, mainly due to insulin deficiency or hyperglycemia occurring under the causation of infection. The main symptoms are dry mouth, flushed face, nausea and vomiting, abdominal pain, deep and fast breathing, and even the smell of rotten apples. In severe cases, there can be life-threatening manifestations, such as faster heart rate, drop in blood pressure, coma, and other changes in mental status. Laboratory tests may reveal elevated blood glucose, positive blood ketone bodies, a significant decrease in carbon dioxide in electrolytes, and a decrease in PH in blood gas analysis. Hyperglycemic hyperosmolar syndrome is another clinical type of acute complication of diabetes mellitus, mainly characterized by severe hyperglycemia, elevated plasma osmolality, and dehydration of the body, and in severe cases, there may also be varying degrees of impaired consciousness or coma, but unlike diabetic ketoacidosis, there are no manifestations of ketoacidosis, such as flushing, nausea and vomiting, and the smell of rotten apples in breathing. Laboratory tests can reveal significantly elevated blood glucose, negative blood ketone bodies, elevated blood sodium and potassium in electrolytes, and normal carbon dioxide. Hypoglycemia, as the name implies, is a drop in blood sugar. For diabetic patients, blood sugar below 3.9 mmol/L can be called hypoglycemia. In addition, the acute complications of diabetes include diabetes with infection, diabetic foot, diabetes combined with acute cardiovascular and cerebrovascular, etc. The main purpose of understanding the acute complications of diabetes is to detect and treat them as early as possible to reduce the harm of diabetes.