Sleeping at night is always thirsty may be caused by open-mouth breathing, but also may be caused by diabetes, uremia, psychogenic polydipsia and other disease factors. 1. Open-mouth breathing: when the weather is dry, people sleep at night with their mouths open to breathe through the mouth, water is evaporated in large quantities, which can lead to the symptom of always thirsty when sleeping at night. In addition, some nasal diseases, such as adenoid hypertrophy, nasal septum deviation, etc., can also induce open-mouth breathing, leading to the symptoms of always thirsty at night sleep. 2. Diabetes mellitus: diabetes mellitus due to osmotic diuresis, resulting in patients with symptoms of polydipsia, polyphagia, polyuria, weight loss, this patient will have an increase in nocturia, which accordingly leads to the symptom of always thirsty at night sleep. 3. Uremia: Uremia is a disease caused by a decrease in the secretion of antidiuretic hormone, patients with this disease will excrete hypotonic urine, and feel thirsty, drink a lot of water, this patient will also have the symptom of always thirsty at night sleep. 4. Mental polydipsia: mental polydipsia is a disorder of thirst due to mental reasons or changes in the regulation of osmotic pressure receptors, and patients with this disease will also experience the symptom of always being thirsty when sleeping at night. In addition to the above factors, other causes can also lead to the symptoms of sleeping at night always thirsty, if the symptoms continue to be unrelieved, you should consult a doctor in time to find out the cause and ask the doctor to deal with it.