Diabetes mellitus is a syndrome caused by various reasons, characterized by elevated blood glucose, and its diagnosis mainly relies on the measurement of blood glucose. In addition, the observation of the efficacy of diabetes treatment mainly relies on blood glucose monitoring, and the adjustment of drugs and treatment plans according to the change of blood glucose, so monitoring blood glucose is indispensable for diabetic patients throughout their life. Patients need to clarify several basic concepts first: 1. Fasting blood glucose: refers to the blood glucose value measured by overnight fasting for more than 8 hours and blood collected before breakfast. 2.Pre-meal blood glucose: refers to the blood glucose measured before breakfast, lunch and dinner. 3.2 hours postprandial blood glucose: the blood glucose measured 2 hours after the first bite of breakfast, lunch and dinner. 4.Random blood glucose: Blood glucose measured at any other time of the day, such as before bedtime, midnight, etc. Blood glucose monitoring several times a day can more accurately reflect the whole picture of the patient’s blood glucose changes, and adjusting the treatment based on only one blood glucose monitoring result often results in deviation. Of course, it is impractical to monitor blood glucose every day, so how to master the time and frequency of self-glucose monitoring? Here are the following points: 1. For patients with stable blood glucose control, the interval of blood glucose monitoring can be lengthened, and the fasting and 2-hour postprandial blood glucose can be measured once a week, and the blood glucose spectrum of 7 points of the whole day can be measured every 2-3 weeks, i.e. the blood glucose before three meals, 2 hours after three meals and before bedtime, and the blood glucose at 3:00 a.m. can be added if necessary. 2.For patients with large fluctuation of blood sugar recently, such as patients with hypoglycemia, patients with drug replacement or dose adjustment, etc., the monitoring frequency should be increased according to the condition, and the whole-day “blood sugar spectrum” should be measured 2-3 times a week. 3. Blood glucose should be tested in time when the symptoms of hypoglycemia appear, and blood glucose should be monitored before and after strenuous exercise. Finally, I would like to emphasize several points of attention in monitoring blood glucose: 1. There are many factors affecting the blood glucose results, such as inconsistency between the code of blood glucose meter and test paper; expired test paper; improper operation method; improper blood collection method; unclean blood glucose meter; long time without calibration of blood glucose meter; insufficient battery power, etc.