Thirst before dawn may be caused by sweat evaporation, too salty dinner, diabetes, dry syndrome and other reasons. 1. Sweat evaporation: after a night’s sleep, due to high ambient temperature, sweat evaporation will lead to water loss in the body, no water supplementation at night, the body’s blood volume is insufficient, the salivary glands secretion of saliva to reduce the amount of dry oral mucosa, before dawn will feel thirsty. 2. Dinner is too salty: dinner ate too salty food, body fluids in the sodium ion is too high, you will feel thirsty. 3. Diabetes: diabetic patients, high blood sugar will cause plasma osmotic pressure increases, plasma osmotic pressure increases and then stimulate the hypothalamus thirst center, will produce the feeling of thirst, there will be the performance of thirst. 4. Dry syndrome: patients with dry syndrome, due to the salivary glands are destroyed by immune cells, resulting in a decrease in salivary secretion, the patient will have the manifestation of thirst. Occasionally before dawn thirst first observation, frequent symptoms of thirst to go to the hospital to check the cause of treatment.