Blood glucose value is the most direct and sensitive indicator that directly reflects the impaired insulin function and treatment effect of diabetic patients. Testing fasting and pre-meal blood glucose is good for discovering hypoglycemia; 2 hours after three meals, blood glucose can better reflect whether eating and hypoglycemic drugs are appropriate; testing blood glucose before going to bed at night can help guide to add meals, prevent nighttime hypoglycemia and ensure sleep safety; testing blood glucose from 1 to 3 am can help discover nighttime hypoglycemia and clarify the real cause of fasting hyperglycemia. 1. Fasting blood glucose Strictly speaking, fasting blood glucose refers to the blood glucose measured before breakfast the next day (usually no more than 8 o’clock at breakfast) after 8 to 12 hours of overnight fasting, and the blood glucose before lunch and dinner is not included in this list. Fasting blood glucose can reflect whether the evening medication can control blood glucose until the next morning, and it is interfered by the dawn phenomenon and the Sumoje response. Fasting blood glucose is also one of the indicators for diagnosing diabetes. There are three common conditions of fasting hyperglycemia: (1) Inadequate medication: characterized by a blood glucose higher than fasting or similar to fasting blood glucose before bedtime, due to insufficient dosage of oral hypoglycemic medication or insulin or excessive food intake in the evening. (2) Dawn phenomenon: After zero o’clock at night, the secretion of growth hormone and glucocortisol increases in normal people, and these hormones have the effect of raising blood glucose, because the amount of growth hormone produced by each person at different stages is different, so the dawn phenomenon does not occur in everyone. Additional blood glucose testing at 3:00 am can reveal normal or high blood glucose. (3) Sumoje reaction: It often occurs at night and is caused by hypoglycemia after overdose of insulin. In order to adjust blood sugar, the body produces a large amount of glucagon, which raises blood sugar. Note that it is best to measure fasting blood glucose at 6 to 8 am, without using hypoglycemic drugs before blood collection, without breakfast and without exercise. If the time of fasting blood sampling is too late, the measured blood glucose value can hardly reflect the patient’s treatment effect, and the result may be high or low. 2. 2-hour postprandial blood glucose 2-hour postprandial blood glucose refers to the blood glucose level 2 hours after meal from the first bite of meal. It mainly reflects the reserve function of insulin beta cells (the body’s ability to secrete additional insulin after increasing sugar load) and the comprehensive efficacy of diet control and drug treatment. The measurement of 2-hour postprandial blood glucose helps in the early diagnosis of type II diabetes because many early diabetic patients do not have high fasting blood glucose, but because their insulin secretion function has been impaired, they respond poorly to high sugar stimulation and thus exhibit significantly elevated postprandial blood glucose. Postprandial hyperglycemia is also an important factor leading to cardiovascular complications of diabetes. Pre-prandial blood glucose refers to the blood glucose before lunch and dinner, reflecting the continuity of pancreatic β-cell secretion function. Pre-meal blood sugar can guide patients to adjust the total amount of food to be eaten and the amount of insulin (or oral medication) before meals. It should be noted that for patients who inject insulin, high pre-meal glucose reflects insufficient insulin dosage before the last meal. For example, high blood sugar before lunch indicates that the insulin dosage before breakfast is insufficient and the dosage needs to be increased. The difference between blood glucose 2 hours after meal and blood glucose before lunch should be greater than 1.0mmol/L in normal people, if the difference is greater than 1.0mmol/L it means good follow-up function of insulin; if the difference is less than 1.0mmol/L it means poor follow-up function of insulin or insufficient dose of medicine. The treatment of preprandial hyperglycemia is the same as postprandial 2 hours hyperglycemia, but the amount of medicine should be increased. 4. Bedtime blood glucose reflects the ability of pancreatic beta cells to control hyperglycemia after eating dinner. The main purpose of monitoring bedtime blood glucose is to guide nighttime meal addition, medication and insulin injection dose to avoid hypoglycemia at night. 5.3am blood sugar Monitoring 3am blood sugar helps to identify whether the cause of fasting hyperglycemia is dawn phenomenon or Sumujer reaction, and the clinical management of these two cases is very different. In general, when dawn phenomenon occurs, it is necessary to consider increasing the bedtime medication dose, while when Sumujer reaction occurs, it is necessary to consider appropriately reducing the bedtime medication dose and adjusting the bedtime meal addition appropriately.