Iron-deficiency anemia (or iron-deficiency anaemia) is a common anemia (low red blood cell or hemoglobin levels) caused by insufficient dietary intake and absorption of iron, and/or iron loss from bleeding which can be from a variety of sources such as intestinal, uterine or from the Urinary tract. Iron deficiency causes approximately half of all anemia cases worldwide, and affects women more often than men. World estimates of iron deficiency occurrence are somewhat vague, but the true number probably exceeds one billion people. This can result if: The body does not make enough red blood cellsBleeding causes loss of red blood cells more quickly than they can be replaced The most significant cause of iron-deficiency anemia in third world children is parasitic worms: hookworms, whipworms, and roundworms. Worms cause intestinal bleeding, which is not always noticeable in faeces, and is especially damaging to growing children.