Fasting blood glucose reflects the level of basal insulin secretion and the amount of food and medication taken the night before is appropriate. Therefore, the concept is to measure blood glucose after an overnight fast of 8 to 12 hours and before 8:00 a.m. the next morning. In some cases, blood glucose measured after 10 o’clock, which is more than 12 hours, or even before lunch or dinner, is not considered “fasting blood glucose”. If the medication is adjusted according to this result, the fasting time may be too long and low, which may affect the dose adjustment of the medication. Of course, it may also be high. Another problem is that the 2-hour postprandial blood glucose is not the blood glucose of the 2 hours after eating, but the blood glucose value measured from the first bite to 2 hours after taking blood. The 2-hour postprandial blood glucose reflects the reserve function of the pancreatic beta cells, and then it can be based on whether the amount of food and medication taken at the meal is appropriate. The concept that many start counting time only after eating is wrong. Under normal circumstances, blood sugar rises to the highest level 0.5 to 1 hour after meal, and blood sugar should basically fall back to the pre-meal fasting level 2 hours after meal.