The common causes of dry mouth at night include the following: I. Physiological causes: 1, before going to bed, such as dinner eat more salty, naturally feel dry mouth at night when you sleep; 2, such as in the room where you live blowing air conditioning, but did not put humidification equipment, resulting in drier air, may also appear at night the symptoms of dry mouth. General will be adjusted or change the external environment, the above symptoms may disappear. Second, the pathological reasons: 1, the night sleep snoring patients, sleep with the mouth open to breathe, resulting in the evaporation of water from the oral mucosa, waking up with a dry mouth; 2, seen in diabetes mellitus as well as uremic patients, due to a variety of reasons, resulting in an increase in the discharge of water from the urinary tract, the body will be dehydrated, the night is usually awakened by thirst, and will be up to drink, and then go to the toilet. However, patients with uremia or diabetes mellitus will have similar symptoms during the day, not only at night.