Iron deficiency is an abnormally low level of iron in the body.
Iron is an essential mineral found in red meat and certain fruits and vegetables. In the body, iron is needed to form myoglobin, a protein in muscle cells, and it is essential for certain enzymes that drive the body's chemical reactions. In the bone marrow, iron is used to make hemoglobin, the oxygen-carrying chemical inside the body's red blood cells. If iron levels fall too low, it causes iron deficiency anemia. When this happens, red blood cells become smaller than normal and contain less hemoglobin.
Iron deficiency can occur in infants, adolescents and pregnant women because of the heavy demands for iron associated with rapid body growth. Iron deficiency is especially common in premenopausal women because of regular loss of iron with menstrual periods.
Iron deficiency also can happen because of any of the following:
An inadequate diet
Poor absorption of iron resulting from the surgical removal of part or all of the stomach or intestine
Inflammatory bowel disease
An intestinal disorder called celiac sprue
Chronic blood loss caused by any of the following:
Abnormally heavy menstrual periods
Bleeding into the urine, which is rare, or into the gastrointestinal tract, which is common; often, the blood loss is so small, it can only be detected with special testing
Excessive blood donation
A parasitic hookworm infestation