Bitter mouth may be caused by drinking too little water or sweating too much, diabetes, dry syndrome, reflux esophagitis, periodontitis and other reasons, need to take metformin and other drugs for the cause of treatment. 1. Drinking too little water or sweating too much: not drinking water for a long time, long time in a hot environment and sweating a lot of factors, physiological causes the body lack of water, so the mouth will be bitter. You need to drink more water and keep your living environment ventilated and at the right temperature. 2. Diabetes: long-term high blood sugar patients with elevated levels of urinary glucose, resulting in osmotic diuresis, the body’s water discharged through the urine, so the mouth will be dry and bitter. You can take metformin, rosiglitazone, pioglitazone and other hypoglycemic drugs, or subcutaneous insulin treatment. 3. Dry syndrome: Salivary glands are attacked by autoantibodies due to autoimmune abnormalities, leading to salivary synthesis and secretion disorders, so the mouth will be bitter. It can be treated with glucocorticosteroids such as prednisone and dexamethasone, and immunosuppressants such as methotrexate and cyclophosphamide. 4. Reflux esophagitis: gastric acid and other stomach contents reflux into the mouth and remain in the mouth, so the mouth will be bitter. You can take omeprazole, ranitidine, domperidone, aluminum magnesium carbonate and other medications. 5. Periodontitis: periodontitis patients with more calculus, and periodontal pockets are very deep, a large number of bacterial reproduction, metabolites may lead to bitter mouth, bad breath, etc., the need for systemic periodontal therapy. Pay attention to the use of drugs under the guidance of the physician.