The current review identifies the root causes of the problem, assesses the clinical impact of iron deficiency and iron deficiency anemia with a specific focus on the condition in developing countries, and outlines the potential solutions to address the problem. Iron deficiency, the most common micronutrient deficiency in the world, results from an imbalance in the access and use of iron in the body. Although it is found in the developing and developed world, it predominantly affects women and children especially those living in poverty. The clinical effects of iron deficiency are profound: mild deficiency results in the loss of concentration in children – affecting their performance at school, and reduces work capacity in adults – affecting their ability to work a full week of work; more profound effects can seriously and permanently damage cognitive development and pose serious health issues in pregnancy and child birth. Despite substantial international efforts to address iron deficiency, the levels have continued to rise over the last decade. As we have the technology to solve this problem, the Copenhagen Consensus Centre (which meets every four years) has identified iron deficiency as the principal health challenge facing the world: the health and economic burden falling predominantly on women of reproductive age.