Bitter mouth and bad breath may be caused by gastroesophageal reflux disease (GERD), gingivitis, periodontitis, etc. Targeted treatments, such as medication and surgery, need to be carried out under the guidance of a doctor. 1. Gastroesophageal Reflux Disease (GERD): patients with gastric dyskinesia and bile reflux, stomach contents often reflux into the esophagus, which not only leads to acid reflux and heartburn, but also bitter mouth and bad taste in the mouth. GERD is mainly treated with medication, commonly used drugs include acid inhibitors (such as cimetidine, ranitidine, etc.), gastrointestinal stimulants (such as domperidone, etc.), antacids (such as magnesium aluminum carbonate, etc.), etc. Surgery can be considered if necessary. 2. Gingivitis, periodontitis: often associated with bacterial infection, bacteria can break down the glycogen in the mouth as well as food residues, resulting in foul odor, which can cause bitter mouth and bad breath. You can use mouthwash (e.g. chlorhexidine gargle, etc.), or consider taking anti-inflammatory drugs (e.g. cephalosporins, metronidazole, etc.), and at the same time, you need to perform a scaling and periodontal scraping to remove dental calculus. It is difficult to judge the disease by this symptom alone, and it cannot be ruled out that it is caused by other factors, such as bile reflux gastritis. It is recommended that the patient consult a doctor in a timely manner to clarify the cause of the disease, and then give targeted treatment, the use of drugs need to follow the doctor’s instructions.