Dry mouth is associated with many diseases, such as dry mouth syndrome or diabetes mellitus. Dry mouth may be a precursor of dry mouth syndrome, a common disease of the oral mucosa, an autoimmune disease, or a decrease in saliva production due to age-related glandular secretion disorders, resulting in dry mouth or difficulty swallowing, and sometimes causing dryness and cracking of the corners of the mouth. In this case, you need to drink more water, eat more vegetables and fruits to replenish vitamins, and if necessary, you need to cooperate with medication. Dry mouth can also be a precursor of respiratory diseases. When inflammation occurs in the respiratory tract, the body eliminates these inflammations by consuming water, making the dehydration in the body more and more severe and causing dry mouth. Dry mouth may be a precursor of diabetes. Diabetic patients often have symptoms of dry mouth and thirst. This condition requires a clear diagnosis and full control of blood sugar. Usually drink more water to reduce the sugar level in the blood and the viscosity of the blood. You should eat lightly and control your diet reasonably to keep your blood sugar stable. Dry mouth may also be an early symptom of hyperthyroidism. Patients with hyperthyroidism also experience dry mouth, so drink more water to replenish the body’s water needs. Therefore, dry mouth may be a precursor of dry mouth syndrome or diabetes, and sometimes it is also related to respiratory diseases and hyperthyroidism.