Drinking a lot of water and still have a dry mouth may be due to diabetes, oral diseases, unscientific drinking water and other reasons, need to be specifically analyzed. 1. Diabetes: diabetic patients with increased blood glucose at the same time due to changes in osmolality leading to increased urination, which will cause more drinking, dry mouth phenomenon. If the blood sugar control is not good, this phenomenon will often exist. 2. Oral disease: drink a lot of water or dry lips, may also be due to insufficient oral care, resulting in oral mucosal damage and other diseases affecting salivary secretion. 3. Drinking water unscientific: some people drink less water, every time you drink a lot of water, this way of drinking water is unscientific, may lead to antidiuretic hormone inhibition, resulting in dry mouth symptoms continue to be unable to relieve the situation. Drinking a lot of water still dry mouth has many other reasons, it is best to go to the hospital in time, under the guidance of the doctor to identify the cause of the disease, and standardized treatment.