The common reasons for frequent dry mouth and thirst are as follows: 1. Frequent dry mouth and thirst may be caused by high temperature, which may lead to the expansion of human capillaries, sweat glands secrete sweat for heat dissipation, and the loss of body fluids, which may lead to the symptoms of dry mouth and thirst, which is a normal physiological reason. 2. Frequent dry mouth and thirst may be caused by electrolyte disorders. The clinical symptoms of electrolyte disorders are dry mouth, thirst, irritability, dizziness, etc., and usually need to relieve electrolyte disorders to improve. Frequent dry mouth and thirst may also be caused by some adverse diseases, such as diabetes mellitus, which can cause abnormal basal metabolism of human body due to high blood sugar in human body, thus causing symptoms of polyuria in human body and excessive fluid loss in human body, which often cause symptoms of dry mouth and thirst in human body, and usually need to treat the original disease to improve.