Dry mouth is characterized by subjective thirst and the desire to drink water, and the symptoms improve slightly after drinking, but soon the thirst starts again. It is important to pay attention to dry mouth caused by stomatitis, diabetes, etc. According to Chinese medicine, dry mouth and thirst are mostly caused by the deficiency of liver and kidney yin and the lack of fluid, or by heat and fluid injury and burning of fluid. The lack of water in the human body causes thirst, and people feel thirsty when the weather is hot, doing heavy physical labor, blood loss, burns, vomiting, diarrhea, and sweating a lot due to high temperature (heat stroke). Dry mouth and unbearable thirst should be distinguished from the following diseases: 1. Dry mouth syndrome Dry mouth is one of the main symptoms of dry syndrome. Its dry mouth is often unbearable, and even if water does not leave the mouth, it does not quench the thirst. Patients have less saliva, swallowing dry food is very difficult, the tongue and corners of the mouth are cracked and painful, and are prone to dental caries. About half of the patients have swollen parotid glands, some patients have symptoms of swollen submandibular glands or nearby lymph nodes, and some patients have joint pain, mostly in the elbow and knee joints. Severe cases may cause damage to kidney tubules, resulting in dangerous consequences such as cardiac arrhythmia. Those who suffer from dry syndrome often have foreign body sensation and burning sensation in their eyes, and their nostrils are dry and easily crusted. The diagnosis of dry syndrome is not difficult, but its dry mouth symptoms are mostly not noticed by patients and doctors, resulting in missed diagnosis and misdiagnosis. 2, diabetes Diabetic patients often have dry mouth, thirst symptoms. The typical symptoms of clinical diabetes can be summarized as “three more and one less”, that is, more drinking, more food, more urine and weight loss. Polyuria includes increased urine volume and increased frequency of urination, the total daily urine volume can reach 3 – 5 liters, or even up to 10 liters. As a result of polyuria, the body loses a lot of water, so the mouth is dry and thirsty and likes to drink more. The amount of water drunk is directly proportional to the blood glucose concentration, the volume of urine and the amount of sugar lost in the urine. As an early sign of diabetes, dry mouth is often overlooked because other symptoms are not typical enough, thus missing a good opportunity for early treatment. The diagnosis of diabetes is relatively easy, and high blood sugar is the main basis for the diagnosis of diabetes. As long as fasting blood sugar and postprandial blood sugar are measured, diabetes can be clearly identified. 3. Hyperthyroidism Hyperthyroidism (hyperthyroidism) can also present with dry mouth. Patients with hyperthyroidism have increased energy metabolism, increased oxygen consumption, increased heat production, and accelerated heat dissipation. Clinical symptoms include dry mouth and sweating, fear of heat, moist and warm skin, enlarged thyroid gland, and protruding eyes. The onset of hyperthyroidism is slow and most patients do not remember the exact time of onset, and the early symptoms are not obvious, so it is easy to be ignored by patients.