Anemia, iron deficiency: Anemia due to inadequate iron. Iron is necessary to make hemoglobin, the molecule in red blood cells that is responsible for the transport of oxygen. In iron deficiency anemia, the red cells are small and pale. Characteristic features of iron deficiency anemia in children include failure to thrive and increased infections. Iron deficiency anemia can be treated with iron supplements and iron-containing foods. Food sources of iron include meat, poultry, eggs, vegetables, and certain cereals. Iron supplements may also be taken, although they should never be given to children without a physician's recommendation.