Iron is essential for most forms of life, including humans. On the other hand, iron is also potentially toxic. Therefore, the control of iron metabolism and maintenance of iron hemostasis is an crucial part of many aspects of human health and disease. Iron deficiency anemia is one of the most common diseases worldwide, but there are also anemias associated with chronic diseases, and other acquired or hereditary defects. Understanding the control of iron metabolism is furthermore important for understanding diseases of iron overload, like hemochromatosis. This booklet is designed for physicians, clinical lab personnel and medical students. It gives an overview about the principles of regulation of iron metabolism and erythropoiesis. In addition, the various disturbances of iron metabolism and the associated clinical findings are described. Special focus lies on the differential diagnosis of the disorders, and the approaches of therapy. Finally, a comprehensive schedule of tests is included available for the determination of iron metabolism-related parameters in serum/plasma and blood, with indication of methodologies applied and reference ranges.