The causes of bitter mouth may be gastrointestinal diseases, liver diseases, gallbladder diseases and other diseases. 1. Gastrointestinal diseases: Bitter mouth in reflux esophagitis is due to the reflux of stomach acid and food into the esophagus; bitter mouth in gastritis may be caused by Helicobacter pylori infection, which can induce halitosis; and the accumulation of food during indigestion can also cause bitter mouth. 2. Liver disease: Hepatitis, when liver cells are destroyed and bilirubin is elevated, is often accompanied by bitter mouth in the morning, and the bitter mouth can be alleviated when hepatitis is in remission. 3. Gallbladder diseases: cholecystitis, gallbladder stones and other diseases may cause bile reflux, bile reflux can cause bitter mouth. When there is a bitter mouth, you can go to the hospital for diagnosis and treatment by a professional doctor.