The first thing to look at is the time of monitoring blood glucose, whether it is fasting blood glucose, postprandial blood glucose, or random blood glucose; secondly, the reference value of blood glucose; and again, whether the measured blood glucose value is within the reference value, whether it is high or low. The normal value of fasting blood glucose is 3.9-6.1mmol/L, and the normal value of blood glucose two hours after meal should be less than 7.8mmol/L. If the normal value of fasting blood glucose is less than 2.8mmol/L, it is called hypoglycemia. Fasting blood sugar greater than or equal to 7.0mmol/L is the diagnostic criterion for diabetes. Two-hour postprandial blood glucose greater than or equal to 11.1mmol/L is also a diagnostic criterion for diabetes mellitus.