The time of defecation after taking Lactulose is related to the patient’s constipation, the patient’s physical condition, the dosage of the drug and so on, usually between 0.5-3 hours of defecation. Lactulose has a laxative effect, constipation patients can be treated by oral lactulose, the onset of action time varies from person to person. Some patients respond faster to lactulose and can experience a bowel movement in half an hour, while some may take 2-3 hours. Some people even take longer, such as 1-3 days before they are able to have a bowel movement. The dose of the drug is also a major factor affecting the time of lactulose defecation, taking a large dose, defecation fast; patients who take insufficient dose, there may be ineffective. Constipated patients need to adjust the habits of life, diet, if necessary, the use of drugs to promote gastrointestinal dynamics and probiotics, such as domperidone, bifidobacteria. When taking lactulose to treat constipation, the cause of constipation should be clarified, and lactulose is prohibited for patients with intestinal obstruction and acute abdomen. Lactulose must be taken under the guidance of a doctor, try to avoid long-term use, otherwise it may aggravate the symptoms of constipation.