Fasting blood glucose is usually recommended to be measured at 6~8 am. Fasting blood glucose is one of the most important indicators for the diagnosis of diabetes mellitus, with a normal range of 3.9~6.1mmol/L. Usually, it needs to be fasted for 8~10 hours, and usually no more food is eaten after 10 o’clock in the evening of the previous day of the test, and measured in the early morning before breakfast. Therefore, it is more appropriate to measure fasting blood glucose at 6-8 a.m. In addition, if the patient is measured later than 8 o’clock, the value may be low due to the patient’s long fasting time, or high due to rebound hyperglycemia from hunger. If the patient’s fasting blood glucose value is abnormal, it is necessary to go to the regular hospital in time.