Mannitol creates a hypertonic environment in the intestinal lumen, which allows water to pass from the tissues into the intestinal lumen, increasing the water content of the feces, which in turn has the effect of helping to expel feces from within the body. The time to have a bowel movement after drinking mannitol varies from person to person, but usually 0.5~1 hour to have a bowel movement, sometimes it may take more than 1 hour to have a bowel movement. 1.0.5~1 hour can have a bowel movement: Normal people who are not troubled by chronic constipation can have a bowel movement in 0.5~1 hour after taking mannitol orally. Because mannitol cannot be absorbed, it creates a hypertonic state in the intestines, causing a bowel movement. 2. 1 hour or more before defecation: for patients with long-term chronic constipation, more than 1 hour after drinking mannitol before defecation. Mannitol after drinking how long can defecate suggest specific advice related to the doctor, the drug needs to be taken under the guidance of a physician, do not take the drug on their own.