Bitter mouth may also be called mouth bitterness, which may be due to long-term smoking and drinking, and the abnormal sensation caused by the ingredients in tobacco and alcohol stimulating the taste buds, or it may be a sign of some diseases. It may be oral disease, stomach disease or liver and gallbladder disease, and it may be caused by diabetes or nerve dysfunction: 1. Oral disease: Poor oral hygiene may cause periodontitis, which brings about symptoms such as bitter mouth or bad breath. Gum or salivary gland infection may also lead to abnormal taste sensation in the mouth; 2, gastrointestinal diseases: abnormal gastrointestinal tract dynamics causing reflux or gastritis caused by Helicobacter pylori infection, gastric ulcer and other diseases may also lead to bad taste or bitter mouth, usually accompanied by epigastric pain or acid reflux heartburn and other symptoms; 3, liver and gallbladder diseases: if there are gallstones or cholecystitis and other diseases causing abnormal bile discharge, or liver diseases such as viral Hepatitis causes damage to liver cells, and bilirubin in the blood can cause symptoms of bitterness in the mouth. Patients with liver and biliary diseases usually also have jaundice or right upper abdominal distension and pain; 4. Diabetes mellitus: Patients with diabetes mellitus are more likely to have bitter mouth if they have poor blood sugar control, resulting in digestive disorders or an increased risk of oral infection; 5. phenomenon.