The reasons for waking up with a bitter mouth include cholecystitis, bile reflux gastritis, depression, hepatitis, periodontitis and so on. 1. Cholecystitis: If bacterial infection of the gallbladder triggers inflammation of the gallbladder, then bile is stagnant in the gallbladder, so the phenomenon of a bitter mouth can occur. 2. Bile reflux gastritis: Because of various factors, bile flows back into the stomach, and then due to nausea and vomiting, bile enters into the mouth, so the phenomenon of bitter mouth occurs. 3. Depression: due to the mental disorder triggered by the endocrine disorders, bile secretion is too much, too much bile will flow back into the mouth and cause bitter mouth. 4. Hepatitis: due to abnormal liver function, the liver metabolizes bile abnormally, triggering bile stasis, which can lead to the phenomenon of bitter mouth. 5. Periodontitis: periodontitis patients have a large number of dental calculus on the tooth surface, and there are deep periodontal pockets, suitable for a large number of bacterial reproduction, sleep in the oral cavity in a relatively anaerobic environment, a large number of anaerobic bacteria reproduction, its metabolites may lead to mouth bitter and bad breath. Finally, please consult your doctor in time for the phenomenon of waking up with a bitter mouth.