Generally speaking, the preoperative control standard for patients’ blood glucose is based on the size of the surgery and the daily blood glucose level of the patient.1. For small and medium-sized surgeries of level I and II, the surgery is less traumatic and the preoperative requirements for blood glucose are lower. Generally, diabetic patients are required to control postprandial blood glucose below 13mmol/L and fasting blood glucose below 10mmol/L for surgical treatment.2. For large-scale surgeries such as level III and IV, the operation time is longer and the trauma of the surgery is greater, and if the patient’s blood glucose is not well controlled after the operation, it will often result in the infection of the incision, or even long-term non-healing. It is recommended that patients should control their blood glucose below 8mmol/L in fasting and 11mmol/L after meal before surgery to make it safer.