In general, a fasting blood glucose of 4.9 mmol/L is normal. But when the elderly fasting blood sugar 4.9mmol / L should be alert to the occurrence of hypoglycemic reaction. Clinically, the normal range of fasting blood glucose is 3.9～6.0mmol/L, for diabetic patients, the goal of glycemic control is generally in the fasting blood glucose 4.4mmol/L～7.0mmol/L. Therefore, the fasting blood glucose of 4.9mmol/L is generally normal. Because of the high risk of hypoglycemia in elderly diabetic patients and their poor ability to perceive hypoglycemia, it is not easy to detect hypoglycemia, so the glycemic control target should be relaxed appropriately. Fasting blood glucose of 4.9 mmol/L should be alerted to the occurrence of hypoglycemic reaction. It is recommended that people with abnormal blood glucose should seek prompt medical attention and be treated accordingly under the guidance of a doctor.