Iron plays a key role in many physiological body life processes, including determination of the correct erythropoiesis. Its lack leads to the development of anaemia, and excess iron can be toxic to the body. Iron homeostasis is supervised by the interaction of many proteins, of which hepcidin plays a very important role and whose modulators are transferrin, ferroportin, and erythropoietin. Important factors modifying iron homeostasis include hypoxia, anaemia, and vitamin concentration as well as acute and chronic inflammatory processes. Hepcidin as an acute phase protein can also be an important element in the diagnosis of infectious chronic diseases, especially as an anaemic determinant of these diseases. Its role in the pathomechanism of acute inflammatory states is not entirely clear.