Lactulose can be drunk on an empty stomach and after meals for the following reasons: 1. The main components of lactulose are fructose and lactose, both of which do not have any stimulation to the gastrointestinal tract, so they can be taken at any time. 2. When lactulose is used in the treatment of habitual constipation, its main role is to promote intestinal peristalsis, increase the osmotic pressure in the intestine, lubricate the intestine and soften the stool, and it is effective when taken on an empty stomach and after meals. 3, lactulose in the treatment or prevention of hepatic encephalopathy, its main mechanism is to reduce or inhibit the formation and absorption of ammonia in the intestinal tract, reduce intestinal pH, there is no difference in the effect of fasting and post-meal consumption. However, in the case of peptic ulcer and erosive gastritis, taking lactulose on an empty stomach may lead to faster intestinal peristalsis and gastrointestinal spasm, causing abdominal pain.