The reasons for getting up in the morning and feeling dry mouth may be the side effects of drugs, head and neck radiotherapy, dry syndrome, open mouth breathing, etc., as follows. 1. Side effects of drugs: (1) Anticholinergic drugs: such as atropine and scopolamine inhibit the secretion of salivary glands by competing with acetylcholine for receptors, leading to a decrease in the amount of saliva causing dry mouth. (2) Antihypertensive drugs: such as rifampicin and methyldopa can inhibit sympathetic nerves, affecting the secretion function of salivary glands and causing dry mouth symptoms. (2) Head and neck radiotherapy: radiotherapy may lead to atrophy or even necrosis of the glands, damage to the membrane of the alveolar cells may lead to changes in the composition of saliva, and damage to the alveolar progenitor cells and stem cells may lead to loss of alveolar function, all of which may cause dry mouth symptoms. 3. Dry syndrome: dry syndrome is an autoimmune disease that accumulates glands all over the body, and the typical phenotype is dry eyes and dry mouth. 4. Open-mouth breathing: when there is upper respiratory tract obstruction, such as adenoid hypertrophy, OSAS and other diseases, will lead to open-mouth breathing, saliva evaporation faster lead to get up in the morning dry mouth. There may be other reasons for waking up in the morning feeling dry mouth, it is recommended to go to the hospital in time. All of the above drugs should be used under the guidance of a doctor, avoid self-medication.