Overview
Iron is needed to help form adequate numbers of normal red blood cells, which carry oxygen throughout the body. Iron is a critical part of hemoglobin, the
protein in red blood cells that binds oxygen in the lungs and releases it as blood travels to other parts of the body. Low iron levels can lead to
anemia, in which the body does not have enough red blood cells. Other conditions can cause too much iron to accumulate in your body. This can produce damage to several organs, including the liver, heart, and pancreas.
Iron status is evaluated by several tests that are not always run together. These include:
- Serum iron - measures the level of iron in the liquid part of your blood.
- Total Iron Binding Capacity (TIBC) - measures the amount of iron that can be carried through blood by transferrin. Transferrin is the protein that transports iron from the gut to the cells that use it. Your body makes transferrin in relationship to your need for iron; when iron stores are low, transferrin levels increase and vice versa. In healthy people, about one-third of the binding sites on transferrin are used to transport iron. This number is called the transferrin saturation.
- Serum ferritin - reflects the amount of stored iron in your body; ferritin is the main storage protein for iron inside of cells.
These tests are often ordered together, and the changes in each can help your doctor to determine if you have a deficiency or excess of iron in your body.
Several other tests can also be used to help recognize problems with iron status.
- Hemoglobin and Hematocrit - These tests are performed as part of a Complete Blood Count (CBC). A low value for either test indicates that a patient has anemia; iron deficiency is a very common cause of anemia. The average size of red cells (Mean Cell Volume or MCV) and the average amount of hemoglobin in red cells (Mean Cell Hemoglobin or MCH) are also measured in a CBC. In iron deficiency, not enough hemoglobin is made, causing the red blood cells to be smaller and paler than normal. Both MCV and MCH are low.
- Zinc Protoporphyrin (ZPP) - Protoporphyrin is the precursor to the part of hemoglobin (heme) that contains iron. If there is not enough iron, another metal, such as zinc, will attach to the protoporphyrin instead. The amount of zinc protoporphyrin in red cells is increased in iron deficiency. ZPP is sometimes used as a screening test, especially in children. However, the test is not specific for iron deficiency, and elevated values must be confirmed by other tests.
- HFE gene test - Hemochromatosis is a common genetic disease that causes your body to absorb too much iron. It is usually due to an inherited abnormality in a specific gene, called the HFE gene, that regulates the amount of iron absorbed from the gut. In people who have two copies of the abnormal gene, too much iron is absorbed, and excess iron is deposited in many different organs, where it can cause damage and organ failure. The HFE gene test uses a sample of blood drawn from your arm to see if you have the mutations that cause the disease (the most common is called C282Y).
