Drinking milk on an empty stomach diarrhea may be caused by lactose intolerance, gastrointestinal dysfunction, milk problems and other reasons. 1. Lactose intolerance: milk contains lactose, part of the human body lacks the enzyme lactase, when fasting can not digest the lactose in milk, resulting in diarrhea. 2. Gastrointestinal dysfunction: some people have gastrointestinal dysfunction, so their digestive system is not good. When gastrointestinal dysfunction, milk can not be digested and absorbed in the gastrointestinal tract, at the same time, fasting leads to fast intestinal peristalsis, milk in the intestinal tract stays for too short a period of time, and the symptoms of diarrhea appear. 3. Milk problems: milk expired or contaminated by bacteria and other pathogens, drinking milk may lead to acute gastroenteritis, there will be empty stomach drinking milk diarrhea symptoms. Drinking milk on an empty stomach diarrhea can usually recover on its own, if the situation is serious, you should seek medical diagnosis. Lactose intolerant people should avoid using milk.