After drinking laxatives for colonoscopy, bowel movement usually starts in about half an hour, and some patients may start to have bowel movement in an hour or two hours. Drinking laxatives is the main measure of colonoscopy, the purpose is to empty the intestinal feces, so as not to block the intestinal tract or adhere to the intestinal wall to block the view of the colonoscope, after drinking laxatives most patients will start to have a bowel movement in about half an hour, but a small number of patients with a slightly lower sensitivity to the drug, it will take one hour or even two hours to start to have a bowel movement. After drinking laxatives start to defecate is similar to the nature of normal stool, but usually not only once, will defecate more than ten times, the stool will gradually become thinner, until completely empty digestive tract contents, so that the colonoscopy vision is clearer, conducive to the physician to observe the intestinal tract.