Diabetic ketoacidosis is often considered clinically when there is a distinct odor of rotten apples in the patient’s exhaled breath. The disease is an acute and critical condition that is more likely to occur in diabetic patients. Its causative factors are most often seen in patients with underlying diabetic disease, resulting from infections, inadequate insulin use or failure to restrict sugar food intake. Patients present with polyuria, increased thirst, marked weakness, loss of appetite, nausea, vomiting, and even coma. Clinically, the patient can be seen to have deep and large Kusmer’s breath, and a distinct odor of rotten apples can be smelled in the exhaled breath. The diagnosis can be further clarified by clinical examination of blood glucose, blood ketones, electrolytes and blood gas analysis in conjunction with the patient’s previous history of diabetes. The main treatment is to provide timely rehydration, hypoglycemia and stabilization of the internal environment. At the same time, the causes of diabetic ketosis should be dealt with.