How long does it take to have a bowel movement after taking Lactulose is related to the dosage, individual constitution and patient’s condition, usually a bowel movement can be achieved in about 2~4 hours after taking it, and some patients may need a longer period of time. Lactulose is a laxative, after entering the intestine, it can retain the water in the intestine, increase the volume of stool, stimulate intestinal peristalsis, and promote the discharge of stool, which is commonly used in the treatment of chronic or habitual constipation and other diseases in the clinic. However, patients may experience adverse reactions such as abdominal pain and bloating, anorexia, nausea and vomiting, and diarrhea when taking it. It should be contraindicated for patients with appendicitis, intestinal obstruction, diarrhea of unknown cause, diabetes mellitus and galactosemia. The onset of lactulose varies from person to person, if the patient’s constipation is not very serious, the patient is more sensitive to lactulose, the onset of action after taking time will be faster, may be in 2~4 hours or so to start defecation. If the patient is constipated for a longer period of time, the stool is more dry, or is not sensitive to Lactulose, the onset of action will be relatively longer, and in severe cases, it may even take 1~3 days to start defecation. In addition, the dose of lactulose and the time of defecation also has a relationship, if the dose is larger, the time of defecation will be relatively early. Lactulose before use is recommended to consult a doctor in advance, strictly in accordance with the doctor’s instructions to take, not self-medication, in order to avoid delays or even aggravate the condition.