Copeptin is important in determining the prognosis of the disease, assigning mortality, setting treatment modalities and increasing the patients' chances for survival in life threatening conditions. Any stress factor activating the hypothalamic-pituitary-adrenal (HPA) axis causes an increase in arginine vasopressin (AVP) plasma concentrations also known as antidiuretic hormone (ADH). Copeptin is derived from preprovasopressin along with neurophysin II and AVP. Copeptin is released in an equimolar ratio to AVP. Various studies have shown copeptin to be an independent indicator in determining the prognosis of the disease and assigning mortality. The purpose of this review was to analyze the advantages of copeptin in patients with life threatening illnesses by reviewing medical data bases.