Bitter mouth may be caused by medication taken before going to bed, oral diseases, bile reflux and other reasons. 1. Drugs taken before going to bed: If the patient has taken drugs before going to bed, such as bifidus tablets, there may be drug residues in the oral cavity, and may produce a bitter mouth when waking up in the morning. 2. Oral diseases: for example, dental caries, when food enters the mouth to grind, caries is easy to residual food debris and bacteria, after the fermentation in the bedtime, may produce bitter mouth feeling when waking up in the morning. 3. Bile reflux: due to factors such as Helicobacter pylori infection or gastric erosion, gastrointestinal dysfunction occurs under the stimulation of gastric acid, causing bile to reflux into the esophagus and mouth, which may result in a bitter mouth when you get up from sleep. In addition to the above, sleeping up bitter mouth can also be seen in other reasons. It is recommended to consult a doctor in time, follow the doctor’s instructions for further examination, clarify the cause with the help of the doctor, and actively cooperate with the doctor to deal with or treat the problem.