The more you drink, the more dry mouth there are many reasons, broadly divided into the following reasons: 1, diabetes mellitus, often have dry mouth, drinking, polyuria and other symptoms, but need to be combined with the monitoring of blood sugar whether to reach the diagnosis of diabetes mellitus. 2, uremia, often have dry mouth, thirst, drinking, polyuria, low specific gravity urine, drinking up to more than 4000ml of water per day, need to be combined with urine specific gravity, anti-diuretic hormone measurement, water prohibition pressin test, etc. 3.Dry mouth syndrome, usually manifested as dry mouth, dry eyes, weakness, low fever, may be accompanied by other systems such as lung, digestive system, nervous system damage, etc., need to combine with anti-nuclear antibodies, SSA, SSB and other immune indicators, as well as imaging examination to clarify the diagnosis. 4.Psychogenic irritable thirst, may appear dry mouth, how to drink water also feel dry mouth, but the examination indicators do not see obvious abnormalities. 5.Other causes, such as electrolyte disorders, hypercalcemia, etc., and endocrine diseases.