Dry mouth and bitterness in bed at night may be related to oral diseases or diseases of the liver and biliary system. Oral diseases, including gingivitis, periodontitis or apical inflammation, can cause dry mouth and bitter mouth at night. Liver disease triggers abnormal bile secretion, or chronic diseases of the gallbladder bile reflux into the stomach or even the oral cavity, especially at night when lying down to sleep reflux is likely to occur, there will be symptoms of dry mouth and bitter mouth at bedtime. Therefore, dry mouth and bitter mouth at night may be caused by gingivitis, periodontitis and other factors, but also may be related to liver disease or chronic inflammation of the gallbladder, you need to go to the stomatology or gastroenterology for further examination.