Iron deficiency is the leading cause of anemia worldwide. Iron deficiency anemia is a condition characterized by blood that is inable to carry the normal amount of oxygen. (This results from the lack of iron, an important metal required for oxygen carriage.) Mild iron deficiency anemia is often asymptomatic, but persistent anemia can result in any number of symptoms, including: * Pale skin color * Blue tinge to sclerae (whites of eyes) * Fatigue * Irritability * Weakness * Shortness of breath * Sore tongue * Brittle nails * Unusual food cravings (called pica) * Decreased appetite (especially in children) * Headache - frontal Physicians often perform a number of tests on patients with suspected anemia. These tests will reveal a low hematocrit, low hemoglobin, and low red blood cell count. In addition, a sample of blood smeared on a slide will show small red blood cells with pale centers. Iron studies will show low serum ferritin, high serum transferrin, and high total serum binding capacity.