It is not normal to have a colonoscopy without diarrhea the first time you drink the medicine. Before doing colonoscopy, you need to take diarrhea-inducing drugs 4-6 hours in advance, commonly used drugs such as compound polyethylene glycol electrolyte dispersal, etc., which can quickly pull out the stool and clean up the intestinal tract, so as to make the results of colonoscopy more accurate. If you do colonoscopy for the first time to drink the medicine does not diarrhea, may be constipation, excessive intestinal contents or insensitive to laxative drugs and so on. If you do colonoscopy for the first time without diarrhea, it is recommended to take a certain amount of diarrhea-inducing drugs again under the guidance of a professional doctor, and to drink a lot of water, which will help the smooth discharge of stools. Otherwise, once the intestinal tract is left with the persistent stool or other intestinal contents, it will affect the accuracy of the colonoscopy results. It should be noted that no food or water should be consumed within 6-8 hours before the colonoscopy. Patients are advised to inform their doctors promptly if they experience any discomfort during the medication period so as not to delay the examination.