Diarrhea after drinking milk may be caused by lactose intolerance, gastrointestinal dysfunction, gastroenteritis, etc., and patients can judge according to their own actual situation. 1. Lactose intolerance: When a patient is lactose intolerant, the patient’s body lacks the enzyme that breaks down lactose, which can lead to diarrhea after drinking milk. 2. Gastrointestinal dysfunction: when the patient has gastrointestinal dysfunction, the gastrointestinal peristalsis is hyperactive, the digestive function is reduced, and the milk cannot be digested and absorbed by the intestinal tract normally, which will easily lead to the symptoms of diarrhea. 3. Gastroenteritis: If the patient drinks unclean milk, it will lead to the entry of pathogenic bacteria into the body, invading the gastrointestinal mucosa, so that the mucosa is damaged, the gastrointestinal tract secretion increases, leading to the symptoms of diarrhea. Drinking milk diarrhea patients, in addition to the above reasons, there may also be other diseases, the patient had better go to the hospital in time for examination, if there is a disease, you can follow the doctor’s advice to timely treatment.