In all cells, iron has essential functions, as energy production and DNA replication; erythroblasts are mostly utilized for haem/haemoglobin synthesis and oxygen transport. The hepcidin–ferroportin axis regulates systemic iron homeostasis, by controlling the iron efflux to plasma from sites of absorption and recycling. Increased iron demand, reduced iron intake, malabsorption and blood loss may lead to negative iron balance, depletion of iron stores and absolute iron deficiency anaemia, the commonest anaemia worldwide. Iron deficiency may be functional as occurs in inflammatory disorders where high levels of hepcidin induce macrophage iron sequestration and iron-restricted erythropoiesis. Anaemia of inflammation is the second most common anaemia worldwide. In clinics distinction between absolute and functional iron deficiency may be blurred and the two conditions may coexist in several common disorders. Diagnosis and treatment of iron deficiency as well as of other rarer iron/haem disorders as sideroblastic anaemia and porphyria are the topics of this chapter.