There is no specific point in time for blood glucose measurement, generally it is fasting and 2 hours after breakfast, lunch and dinner, and if necessary, it can also be measured before three meals and before bedtime. Fasting blood glucose refers to the blood glucose measured in the early morning fasting after 8-10 hours without any food intake, which can reflect the basic secretion function of pancreatic islet β-cells, and it is the most commonly used testing indicator for diabetes, and the normal range of fasting blood glucose is 3.9-6.1 mmol/L. The normal range of fasting blood glucose is 3.9～6.1mmol/L. Postprandial blood glucose is generally required to be measured 2 hours after breakfast, lunch and dinner, which is 2 hours from the first bite of the meal, reflecting the reserve function of pancreatic β-cells, and also judging the control of blood glucose by hypoglycemic drugs. The normal 2-hour postprandial blood glucose level should be less than 7.8 mmol/L. Patients with unstable blood glucose control should have a blood glucose level of 7.8 mmol/L or less. Patients with unstable blood glucose control also need to monitor blood glucose before breakfast, lunch and dinner, as well as before bedtime and at night. The specific time needed to measure blood glucose should be carried out under the guidance of the doctor.