Bitter and dry mouth in the morning can be caused by physiological and etiological reasons (oral diseases, stomach diseases, etc.). 1. Physiological reasons: the human body in the night after sleep, metabolism slows down, saliva secretion in the mouth is less, thus causing the phenomenon of getting up in the morning bitter and dry mouth. 2. Pathologic causes: (1) oral diseases: such as periodontitis, bacteria invade the gum tissue, thus causing inflammation. Clinical symptoms such as bitter mouth, dry mouth and bad taste in the mouth may also occur. (2) Stomach diseases: gastritis, gastric ulcers and other gastrointestinal diseases can lead to weak gastrointestinal digestion, causing indigestion, easy to belching (hiccups), acid reflux, bitter mouth, dry mouth and other symptoms. Bitter and dry mouth in the morning may have other reasons, it is recommended to go to the regular hospital in time to do further examination for targeted treatment.