Iron, a mineral, functions primarily as a carrier of oxygen in the body, both as a part of hemoglobin in the blood and of myoglobin in the muscles. Most people get enough iron in their diet, but chronic bleeding from any cause, including menstruation results in iron loss which may exceed intake, resulting in an additional requirement. A shortage of iron is most commonly evidenced by iron-deficiency anemia. However, body stores of iron must be significantly depleted before anemia begins to develop.