Glucose can be drunk before gastroenteroscopy, but should not exceed 200 ml, and drinking glucose is not routinely recommended as a means of preoperative preparation. The gastrointestinal tract needs to be kept clean before gastroenteroscopy to facilitate gastrointestinal observation. Common preoperative preparations for gastroenteroscopy include discontinuation of medications, preoperative fasting and gastrointestinal preparation. 1. Discontinuation of medicines: anticoagulant and antiplatelet aggregation drugs, such as aspirin, warfarin, clopidogrel, etc., need to be discontinued 5 to 7 days before the examination. 2. Preoperative fasting: you need to eat a light diet the day before the examination, avoiding high-fiber foods and foods with high fat content to prevent the gastrointestinal tract from emptying. After dinner on the day before the examination and before the operation on the next day, you need to abstain from food and drink. If you are intolerant to hunger, you can drink sugar water, but glucose is not routinely recommended. 3. Gastrointestinal preparation: If the colonoscopy is performed in the morning, you need to take a laxative the night before to empty the intestines. Depending on the time of the procedure, the laxative can be taken as a single dose or in two separate doses. In addition, those with delayed gastric emptying will need to fast longer. Patients who have a late procedure the next day may be given parenteral nutritional support if necessary, but not oral glucose, to prevent interference with the gastroenteroscopy.