The most common cause of anemia is iron deficiency, followed by anemia of chronic disease, which is due to an inflammatory reaction in chronic diseases such as heart failure, renal failure, rheumatoid diseases and cancer. Also from the therapeutic point of view, it is useful to divide iron deficiency anemia into two forms: absolute and functional iron deficiency. Absolute iron deficiency is characterized by low iron stores and low total iron. In functional iron deficiency, a sufficient amount of storage iron is present, but it cannot be mobilized. Therapy of iron deficient anemia should always eliminate the underlying cause. The goal of therapy is sustained normalization of hemoglobin concentration and total body iron. Therapy for absolute iron deficiency focuses on improving iron stores, eliminating chronic blood losses, and optimizing iron absorption via an iron-rich diet and iron supplementation. In the case of functional iron deficiency with inflammation present, IV iron supplementation is recommended in certain situations in addition to treatment of the underlying disease, especially in patients with cancer.