Dry and bitter mouth after waking up from sleep may be due to physiologic and pathologic causes. Including bad habits, dry syndrome, bile reflux gastritis and so on. 1. Physiological causes: If there are bad habits such as staying up late, not eating on time, overeating, eating too salty, etc., it may affect the normal metabolism of the body, resulting in dry and bitter mouth after waking up from sleep. It is recommended that the patient regular routine, adjust the lifestyle, eat more fresh vegetables and fruits, so as to improve the situation of waking up with a dry and bitter mouth. 2. Pathologic causes: (1) dry syndrome: dry syndrome may be genetic or infectious reasons, and the onset of the disease is more insidious, will cause damage to the patient’s gland secretion function, so that the patient has a dry and bitter mouth, resulting in the patient woke up with a bitter and dry mouth. With the development of the disease, it may even cause salivary gland inflammation, dry eyes and dry skin mucosa. (2) Bile Reflux Gastritis: Bile Reflux Gastritis may be caused by abnormal pyloric structure or biliary diseases, if bile flows back into the mouth, it will cause bitter mouth, and after falling asleep, it may also lead to a decrease in saliva secretion in the oral cavity, making the patient wake up with a bitter and dry mouth, and accompanied by indigestion. In addition, waking up with a dry and bitter mouth can also be seen in other diseases, such as discomfort, it is recommended that patients go to the hospital in time.