Low blood glucose indicates that the patient may have some kind of factor that causes low blood glucose. There are more causes of low blood glucose, such as insulinoma and hypoglycemic drugs. Hypoglycemia is a clinical syndrome in which plasma glucose level decreases due to a variety of etiological factors, thus causing corresponding symptoms and signs. Clinically normal people with fasting blood glucose lower than 2.8mmol/L is called hypoglycemia. In general, the plasma glucose level that causes hypoglycemia ranges from 2.8 to 3.9 mmol/L. In most patients, after the blood glucose concentration increases to the normal value, the corresponding symptoms and signs disappear. Patients with mild-to-moderate hypoglycemia can be relieved after oral intake of foods such as candy and bread; patients with severe hypoglycemia should be given glucose solution intravenously immediately. Patients with severe hypoglycemia should be injected with glucose solution intravenously immediately. In case of unexplained hypoglycemia, the patient should go to the hospital immediately for appropriate examination and treatment according to the doctor’s instructions.