If a patient presents with dry mouth but not thirst, the cause needs to be discussed from both Chinese medicine and Western medicine. First, from the perspective of Chinese medicine, the most common cause is physical deficiency, often due to kidney yin deficiency and lung deficiency, which leads to dry mouth, but not necessarily to irritable thirst. Secondly, from the perspective of Western medicine, the most common factor of dry mouth but not thirst is endocrine and metabolism, the most common diseases such as hyperthyroidism, in the case of hyperthyroidism patients will have dry mouth, but if there is no obvious kidney hypofunction, there is no obvious diuretic effect, and only clinical symptoms of dry mouth will appear at this time. In diabetes mellitus, dry mouth can also occur, and there is also a thick white tongue coating and little fluid, but if there is no certain kidney damage, no diabetes mellitus combined with nephropathy, and there is no obvious diuretic effect, there will be a dry mouth but no thirst.