Iron plays a key role in most of the body’s metabolic processes. Its deficiency leads to serious consequences, posing a threat to health and life. Iron deficiency most often manifests itself as microcytic anemia, which is diagnosed in over 1.74 billion people worldwide. While the need to treat every form of anemia is beyond doubt, in recent years, thanks to the emergence of safe and effective forms of iron, recommendations have also begun to propose treatment of iron deficiency, even in the absence of anemia. The article discusses the most common causes of iron deficiency and the standards of diagnostic and therapeutic procedures.