4-6 hours. Senna granules is a kind of Chinese medicine commonly used in clinical practice, mainly used for the treatment of dry stools, defecation difficulties, etc., as well as antibacterial, antiseptic, antispasmodic and other effects. Senna granules can make the peristaltic movement of the large intestine rapidly elevated in a short period of time, thus producing a large amount of secretion and smooth bowel movement. Senna is more potent and usually results in a bowel movement 4-6 hours after taking it, and patients may also experience diarrhea the first time they take it. If there is difficulty in defecation, senna granules can be regulated under the guidance of a doctor to solve the problem of constipation. Constipation can also be achieved by maintaining a good daily routine, paying attention to the diversity of dietary structure, increasing the intake of dietary fiber, and enhancing physical exercise to promote gastrointestinal peristalsis, and to develop the habit of regular bowel movements.