Common causes of diarrhea and bitter mouth include drug stimulation, bile reflux and acute gastroenteritis. 1. Drug stimulation: some drugs taste bitter, because of the strong bitter stimulation of the drug, can lead to the patient’s mouth bitter. At the same time, the stomach and intestines are easily irritated, then diarrhea. 2. Bile reflux: When patients suffering from cholecystitis, gastroesophageal reflux disease and other diseases have bile reflux into the stomach, it can stimulate the gastrointestinal tract to speed up peristalsis, resulting in diarrhea. If the food mixed with bile in the stomach refluxes upward, it will cause bitter mouth. 3. Acute gastroenteritis: The attack of acute gastroenteritis due to poor diet, cold abdomen or bacterial infection will cause diarrhea due to intestinal spasm. If the celiac disease in the gastrointestinal tract rises to the esophagus or throat, there will be a sour and bitter taste in the mouth. Patients with persistent diarrhea and bitter taste in the mouth are advised to seek professional medical help.