If you have bitterness in your mouth, you should pay attention to whether there is a cause of bile reflux or abnormal infection in the mouth, such as gingivitis, periodontitis, mouth ulcers, etc. Certain digestive malfunctions, stomach disorders, as well as smoking, drinking, stress, and staying up late can cause bitterness in the mouth, and need to be investigated one by one. The first step is to determine the results of gastroscopy to see if there is bile reflux gastritis and to clarify whether the bitterness in the mouth is due to bile reflux. It is also necessary to improve oral hygiene, actively take care of the mouth, and use mouthwash if necessary to see if the symptoms of bitterness in the mouth are relieved. Diet should include more fresh vegetables and fruits, less high-fat, high-cholesterol, greasy, fried, spicy and stimulating foods, and abstain from smoking and alcohol. After a comprehensive treatment, see if the bitter mouth symptom is relieved.