The bitterness in the mouth in the morning is caused by mouth ulcers, gastroesophageal reflux disease, gallbladder disease, etc., as follows: 1. People with mouth ulcers will wake up in the morning with a bitter mouth, mainly because the inflammation stimulates the taste nerve of the patient, resulting in abnormal nerve function and delusion, which will be accompanied by oral pain and sensitivity to sweet and salty food. 2. Reflux disease will appear in the attack of gastrointestinal reflux, so the contents of the duodenum and stomach will reflux into the esophagus, because the contents are mixed with part of the bile and digestive juices, so when the reflux phenomenon, the mouth will exist a bitter taste. 3, gallbladder diseases mainly include common bile duct blockage, cholecystitis, gallstones and other diseases, these diseases in the attack, not only will lead to severe upper abdominal These diseases not only cause severe pain in the upper abdomen, but also affect the excretion of bile, and in traditional Chinese medicine, bile leakage is bitter in the mouth, so most of these people will have a bitter mouth, especially in the morning when they wake up.