Fasting blood glucose reflects the level of basal insulin secretion and that the amount of food and medication consumed the night before is appropriate. Therefore, the concept is to fast overnight for 8 to 12 hours and then take a blood test before 8:00 am the next morning, so that the blood glucose measured is the “fasting blood glucose”. In some cases, the blood glucose is taken after 10:00 a.m., which is more than 12 hours, or even before lunch or dinner, which is not considered as “fasting blood glucose”. If this result is used to adjust the medication, it may be low because of the long fasting time, which may affect the dosage adjustment of the medication. Of course, it could also be high. Another problem is that the 2-hour postprandial blood glucose is not the blood glucose of 2 hours after eating, but refers to the blood glucose value measured from the first bite of food to 2 hours after blood collection. The 2-hour postprandial blood glucose reflects the reserve function of pancreatic β-cells, and then can be based on whether the meal was eaten and whether the amount of medication was appropriate. Many people start counting the time after the meal, which is a wrong concept. Under normal circumstances, blood glucose rises to the highest level 0.5 to 1 hour after the meal, and blood glucose should basically fall back to the fasting level before the meal 2 hours after the meal.