The use of copeptin as diagnostic marker for the determination of the release of vasopressin, especially in connection with disorders associated with non-physiological alterations of vasopressin release from the neurohypophysis, especially for detection and early detection, diagnosing and monitoring of the course of cardiovascular diseases, renal and pulmonary diseases as well as shock, including septic shock, sepsis and diseases/disorders of the central nervous system and neurodegenerative diseases.