Thirst (polydipsia) is the desire to drink water in large quantities, which is accompanied by subjective sensations of dry mouth. A symptom can occur with various endocrine diseases, increased fluid loss during breathing and sweating, pathologies of the liver and kidneys. To determine the causes of thirst and a feeling of dry mouth, ultrasound of the internal organs, X-ray examination, laboratory blood and urine tests, and hormone tests are performed. To eliminate pathological polydipsia, drug correction of the underlying disease that caused the manifestations of thirst is necessary.