Bitter mouth in the morning may be caused by physiological factors such as improper diet, improper oral cleaning, or diseases such as cholecystitis and reflux esophagitis. 1. Physiological factors: If you eat too much bitter food, such as bitter melon, black coffee, or spicy and stimulating food the night before, as well as improper oral cleansing, it may lead to the accumulation of oral residues, and the situation of getting up in the morning with a bitter mouth. 2. Pathological factors (1) Cholecystitis: Cholecystitis is mainly caused by bile duct obstruction, bile stasis and secondary infection. Patients may have sudden right upper abdominal cramps radiating to the right shoulder and back, accompanied by anorexia, nausea, vomiting and other symptoms, which may be manifested as bitter mouth in the morning. (2) Reflux esophagitis: Reflux esophagitis may be caused by the decrease of anti-reflux function, the decrease of esophageal clearing ability, and esophageal sensory abnormalities. Patients may suffer from reflux, which is characterized by the effortless influx of stomach contents into the pharynx and mouth, and some patients may suffer from bitter mouth in the morning. There are many causes of bitter mouth in the morning, and it is recommended that patients consult a doctor in time to find out the cause of the disease.