Most doctors’ experience is that the perioperative glycemic control goals for non-fine surgery are fasting blood glucose <8 mmol/L and random blood glucose <12 mmol/L. Fine surgery requires fasting blood glucose <7 mmol/L and random blood glucose and 2-hour postprandial blood glucose <10 mmo/L. When diabetic patients are to undergo ophthalmic surgery, their blood glucose should be controlled closer to normal. The blood sugar should be controlled closer to the normal level. For patients with elective surgery, preoperative complications such as cardiovascular disease, autonomic neuropathy and nephropathy should be thoroughly evaluated. Preoperative fasting blood sugar should be controlled below 7.8 mmol/L and postprandial blood sugar below 10.0 mmol/L. For those who have uncontrolled blood glucose but intend to perform emergency surgery, blood glucose, electrolytes, blood gas analysis and urinary ketone bodies should be monitored before surgery, and surgery should be performed only after correction of ketoacidosis and electrolyte disturbance. Severe ketoacidosis or hyperosmolar coma is a contraindication to surgery, and surgery should be performed only after blood glucose is reduced by 13.9 mmol/L and vital signs are stabilized. When diabetic patients without diabetic ketoacidosis are to undergo emergency surgery, it is advisable to control blood glucose below 13.9 mmol/L. 3. Perioperative blood glucose monitoring (1) Preoperative. In order to enable patients to safely pass the operation period, adequate preoperative preparation must be made. First of all, we should grasp the severity of the patient's condition, understand in detail the function of each important organ, and evaluate the metabolic disorder, electrolyte and acid-base balance. For diabetic patients who are to undergo elective surgery, they should be admitted to the hospital 5-7 days before surgery for relevant preoperative preparations. Those who need general anesthesia for major surgery (such as esophageal, gastric or pancreatic surgery) should be handled more carefully. Some patients with diabetic ketoacidosis may have acute abdominal manifestations, which should be carefully differentiated to avoid misdiagnosis. Monitor blood glucose seven times a day before surgery, i.e. before three meals, two hours after three meals and before bedtime. (2) Morning of the operation day. Keep the patient emotionally stable, monitor fasting glucose, electrolytes and urinary ketone bodies. A catheter should be left in place for large and medium-sized surgeries, and urine volume or urine ketone bodies should be observed intraoperatively so that they can be handled accordingly. (3) During surgery. Try to shorten the operation time, reduce the length of incision, avoid excessive width of subcutaneous free, and reduce the stimulation to the patient. Avoid the application of drugs that excite sympathetic nerves and promote glycogenolysis, such as epinephrine, atropine, ether, morphine, m-hydroxylamine and glucocorticoids during anesthesia. Adverse factors such as too shallow anesthesia, poor nerve block and hypoxia should be avoided. Intraoperatively, finger blood glucose is usually measured once every hour, and for patients with hypoglycemia, the blood glucose concentration should be rechecked after 30 minutes. If it is a non-major operation and the patient's blood glucose level has been stable, the blood glucose can be measured once every 2~4 hours, and the urinary ketone body should be monitored every 2 hours for those with catheterization in major surgery. (4) Postoperative. Patients should continue to receive postoperative blood glucose monitoring, generally every 2~4 hours, especially attention should be paid to whether hypoglycemia occurs in patients who fast after surgery. For diabetic patients who intend to undergo larger surgery and whose preoperative blood glucose control is not up to standard, multiple (3 or 4) subcutaneous insulin injections should be used to effectively control blood glucose. For diabetic patients who need to fast before surgery and the surgery is expected to take a long time, basal insulin [such as medium- or long-acting insulin (0.1 to 0.2 U/kg body weight)] can be given, or 5% to 10% glucose solution and insulin (0.2 to 0.4 U of insulin per gram of glucose) can be administered intravenously until the end of the surgery. The ratio of insulin to glucose varies in different cases, as detailed in the table. Intraoperative blood glucose changes are closely monitored, and when blood glucose is ≥13.9 mmol/L, then the sedative glucose and insulin are stopped and replaced by sodium chloride insulin solution without glucose; if blood glucose is at 10.0~13.9 mmol/L, then the insulin dose needs to be increased appropriately, and subcutaneous injection of short-acting or fast-acting insulin can be chosen. However, during surgery, it should be considered that the absorption of insulin may be unstable after subcutaneous injection, so those with unstable blood glucose before surgery can also receive insulin pump therapy, thus reducing intraoperative blood glucose fluctuations, and closely monitoring blood glucose levels and adjusting insulin doses in a timely manner. For diabetic patients who need to continue fasting after surgery, they should continue to receive basal insulin therapy, and can choose medium-acting or long-acting insulin or insulin pump therapy. If intermediate-acting or long-acting insulin is chosen, it should be injected subcutaneously every 12 hours or 24 hours, respectively. For diabetic patients who resume eating, short-acting or fast-acting insulin can be injected subcutaneously before meals and the premeal insulin dose can be adjusted according to the postprandial blood glucose level; for patients with fasting blood glucose ≥7.0 mmol/L at breakfast, medium-acting or long-acting insulin can be given at bedtime (21:30~22:00) and the bedtime insulin dose can be adjusted according to the fasting blood glucose level, or an insulin pump can be selected and the premeal insulin dose can be adjusted according to the postprandial blood glucose level to adjust the preprandial insulin dose.