Iron (Fe) is a necessary mineral for the proper function of hemoglobin, (protein in red blood cells that carries oxygen). It is also needed for proper muscle and organ function. About three-fourths of the body's iron is bound to hemoglobin in red blood cells, while the rest is either 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. In the bone marrow, iron is stored and used as needed to make new red blood cells.

Iron studies are usually done to define the following:

• The amount of iron bound to transferrin. This is called the serum iron measurement.
• The amount of iron needed to bind to all of the transferrin in a certain amount of blood. This value is called the total iron-binding capacity (TIBC) and is an estimate of the amount of transferrin in the blood.
• The percentage of sites on transferrin that have iron bound to them. This is called the amount of transferrin saturation and equals the serum iron measurement divided by the TIBC.

The original source of all the body's iron is food (such as liver and other meat, eggs, fish, and leafy green vegetables). Generally, only about 5% to 10% of the iron in food is actually absorbed, unless the body needs more because of rapid growth (such as during adolescence, pregnancy, breast-feeding, or at times when there are low levels of iron in the body (such as after bleeding).

Healthy adult men usually 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. Therefore, men rarely develop an iron deficiency. Women, however, can lose large amounts of iron because of menstrual bleeding, during pregnancy, or while breast-feeding. Therefore, women are more likely than men to develop an iron deficiency and may need to take an iron supplement. Iron deficiency in men and women past menopause usually is related to abnormal bleeding.

This test is done on a blood sample taken from a vein.

Iron (Fe)
Results

Normal

Normal results may vary from lab to lab.

Abnormal

The values for serum iron, total iron-binding capacity (TIBC), and transferrin saturation are used mainly to determine if a low amount of iron is due to iron-deficiency anemia or another condition, or if a high amount of iron is due to hemochromatosis or another condition.

• A high serum iron value can indicate hemolytic anemia, thalassemia, cirrhosis, hemochromatosis, lead poisoning, or an excessive use of iron supplements.
• A high value for serum iron, a very high value for transferrin saturation, and a slightly low total iron-binding capacity (TIBC) may indicate the presence of iron overload (hemochromatosis). Iron overload can result from an inherited condition, from some types of anemia in which iron stays in the body, from liver disease or excessive use of iron supplements, or from having many blood transfusions. High levels of iron can damage many organs, such as the heart, pancreas, and testicles.
• Low serum iron and transferrin saturation values and a high TIBC value may indicate iron-deficiency anemia, most commonly from a diet low in iron (iron-deficient diet), bleeding, cirrhosis, or poor absorption of iron by the intestines.
• A low serum iron value when the other two values are low or normal indicates anemia caused by a long-term disease, such as cancer, rheumatoid arthritis, kidney failure, or a severe infection. This is called anemia of chronic disease and is different from iron-deficiency anemia. A ferritin test can be used to further investigate these results.