Laxatives need to be taken 4-6 hours in advance before the colonoscopy. Generally you need to take diarrhea-inducing medications such as mannitol, magnesium sulfate, and polyethylene glycol electrolyte dispersions 4-6 hours ahead of time before a colonoscopy, as well as drinking plenty of water and exercising to promote bowel movements. Bowel cleansing is a very critical step before doing a colonoscopy. If there is feces left in the intestines, the colonoscopy will affect the observation, and it is not easy to develop intestinal lesions, resulting in inaccurate results. It should be noted that before doing colonoscopy, but also 2-3 days in advance to eat light, easy to digest, do not leave residue of food, it is best not to eat watermelon, dragon fruit, etc., to avoid the examination is mistaken for a bleeding point, affecting the judgment of the examining physician. It is recommended that patients take laxatives as prescribed by the doctor before the colonoscopy so as not to affect the results of the examination.