Dry mouth can be caused by a variety of conditions, possibly due to diabetes, a typical symptom of diabetic patients is three more and one less, i.e., more drinking, more urination, more eating, and weight loss. Due to diabetes-induced polyuria, the body loses a lot of water, which often leads to a dry mouth. Dry mouth can also be caused by thyroid disorders. Hyperthyroidism is typically characterized by increased heat production and rapid heat dissipation, which can be manifested by excessive sweating, thirst, and dry mouth. Dry mouth can also be caused by dry syndrome, which is an immune disorder, and one of the common symptoms is frequent thirst and itchy skin. There are many causes of dry mouth, so it is recommended to go to the hospital in time to determine the cause of the disease and timely treatment.