Dry mouth may be caused by dehydration, hyperthyroidism, diabetes, dry syndrome. 1. Lack of water: due to excessive exercise or hot weather and other reasons will make the body sweat more, the body loses a lot of water and can not replenish water in a timely manner, easy to cause thirst, dry mouth. 2. Hyperthyroidism: female pregnancy is prone to hyperthyroidism, which is characterized by mood swings, hair loss, weakness, sweating, etc. Sweating will also cause dry mouth. 3. Diabetes: The blood sugar level in the body of a diabetic is high, and the patient is prone to increased urination. Frequent urination will make the body lose more water, and patients often feel thirsty. 4. Dry syndrome: Dry syndrome is mainly caused by damage to the salivary glands and lacrimal glands. The most common symptoms are dry mouth and dry eyes, and other symptoms can also be manifested as dental caries and loss of taste. If patients still feel dry mouth after drinking a lot of water, it is recommended to go to the hospital for appropriate examination to clarify the cause of the disease, and targeted treatment under the guidance of the doctor.