Pre-meal blood sugar generally refers to fasting blood sugar, while post-meal blood sugar often refers to blood sugar measured 2 hours after breakfast, lunch and dinner. It is a common phenomenon that the pre-meal blood sugar is higher than the post-meal blood sugar, which is mostly related to the effect of glucagon, low blood sugar at night and the influence of drugs, etc. 1. The effect of glucagon: Generally speaking, the secretion of adrenocorticotropic hormone is rhythmically secreted, reaching the peak at 8:00 in the early morning, with a low value at 12:00 at night and a second small peak at 5:00 in the afternoon, and the peak secretion at 5:00 is lower than the peak secretion at 8:00. The peak secretion at 5:00 is half of the peak secretion at 8:00. Since glucagon starts to be secreted in the morning under the influence of adrenocorticotropic hormone secretion rhythm, preprandial blood glucose is higher than postprandial blood glucose. After the occurrence of hypoglycemia, the glucose hormone secretion, together against the effect of insulin, and then the symptoms of high blood sugar before meal than after meal; 3, drug influence: high blood sugar before meal than after meal may be that the drugs used by diabetic patients are not very suitable, using more drugs, the dose is high, easy to appear hypoglycemia. At the same time, if the dose of the drug used at night is too small, it will easily lead to the drug concentration not reaching the morning, resulting in the rise of fasting blood sugar in the early morning. In addition, if the insulin used by the patient is ultra-short-acting insulin, this situation may also occur due to the fast onset and short duration of this drug.