Clinically, diabetic patients with blood sugar lower than 3.9mmol/L is called diabetic hypoglycemia, which is different from the standard of normal population hypoglycemia, which is blood sugar lower than 2.8mmol/L. Diabetic patients with blood sugar lower than 3.9mmol/L will show sympathetic excitement, such as panic, hand trembling, sweating, hunger, some patients will have blurred vision, weakness and other symptoms. In order to correct the symptoms of hypoglycemia, it is necessary to give carbohydrates, such as cookies, sugar cubes and fruit juices, and at the same time, pay attention to finding the cause of hypoglycemia. If elderly patients with diabetes are less sensitive to hypoglycemia response, blood sugar below 3.9mmol/L often has no symptoms of sympathetic excitation, called asymptomatic hypoglycemia, and patients are at risk of hypoglycemic coma. Therefore, diabetic patients should lower their sugar safely in the process of treatment to avoid hypoglycemia and avoid blood sugar lower than 3.9mmol/L, especially for elderly diabetic patients, blood sugar is not easy to be too low.