A dry tongue and dry mouth can be a sign of diseases such as diabetes and dry syndrome. It may also be related to eating too salty or drinking too little water. 1. Diabetes mellitus: mainly manifested as dry mouth and throat, polyphagia and emaciation, etc. This symptom is mainly due to the insufficient secretion of insulin, which can not break down the excess glycogen, the plasma osmotic pressure increases, and polyuria, which leads to the appearance of a dry tongue and a dry mouth. 2. Dry syndrome: due to the disorders of immune function, the salivary gland function will be impaired, saliva secretion is seriously reduced, which leads to very serious dry mouth and dry tongue. 3. Physiological factors: Eating too salty or drinking too little water can cause dry mouth and dry tongue, and the symptoms can be improved by eating a light diet and drinking more water. It is recommended that patients who often have dry tongue and dry mouth should actively go to regular hospitals to do a comprehensive examination, discover the disease early, make a clear diagnosis, and do regular treatment under the guidance of professional doctors.