An iron test checks the amount of iron in the blood to see how well iron is metabolized in the body. Iron (Fe) is a mineral needed for hemoglobin, the protein in red blood cells that carries oxygen. Iron is also needed for energy, good muscle and organ function.
About 70% of the body's iron is bound to hemoglobin in red blood cells. The rest is bound to other proteins (transferrin in blood or ferritin in bone marrow) or stored in other body tissues. When red blood cells die, their iron is released and carried by transferrin to the bone marrow and to other organs such as the liver and spleen. In the bone marrow, iron is stored and used as needed to make new red blood cells.
The source of all the body's iron is food, such as liver and other meat, eggs, fish, and leafy green vegetables. The body needs more iron at times of growth (such as during adolescence), for pregnancy, during breast-feeding, or at times when there are low levels of iron in the body (such as after bleeding).
Healthy adult men get enough iron from the food they eat. Men have enough reserves of iron in their bodies to last for several years, even if they take in no new iron. Men rarely develop an iron deficiency because of their diets. But women can lose large amounts of iron because of menstrual bleeding, during pregnancy, or while breast-feeding. So women are more likely than men to develop an iron deficiency and may need to take an iron supplement. Iron deficiency in men and in women past menopause is often from abnormal bleeding, often in the gastrointestinal tract, such as from stomach ulcers or colon cancer.
The iron test checks the:
- Amount of iron bound to transferrin in the blood (serum).
- Amount of iron needed to bind to all of the transferrin. This value is called the total iron-binding capacity (TIBC).
- Percentage of transferrin with iron bound to them. This value is called transferrin saturation.