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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 breastfeeding, 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 breastfeeding. 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.
Why It Is Done
A test for iron is done to:
- Check for too much or too little iron in the blood.
- See if your diet is providing enough iron.
- Find out if treatment to keep the right amount of iron in your blood is working.
How To Prepare
- Do not take iron supplements for 12 hours before your iron test.
- Iron levels change throughout the day. So it's best to do iron tests in the morning, when iron levels are highest.
How It Is Done
A health professional uses a needle to take a blood sample, usually from the arm.
How It Feels
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
Values that may be checked include serum iron, total iron-binding capacity (TIBC), and transferring saturation.
High and low values
The values for serum iron, total iron-binding capacity (TIBC), and transferrin saturation are used to see if a low amount of iron in the body is from iron deficiency anemia or another condition. The values are also used to see if a high amount of iron is caused by hemochromatosis or another condition. Other conditions that affect iron, TIBC, and transferrin saturation levels include:
- Hemolytic anemia. This causes a low amount of oxygen-carrying hemoglobin found in red blood cells. The iron levels are often normal.
- Thalassemia. This is a blood disorder that runs in families (inherited). It changes how the body makes hemoglobin. The iron levels are often normal, but ferritin levels may be high if the person has had a lot of blood transfusions.
- Cirrhosis. This is a condition that occurs when inflammation and scarring damage the liver.
- Lead poisoning. This develops from months or years of exposure to small amounts of lead in the environment.
- Iron deficiency anemia. This occurs when low iron levels cause a low amount of oxygen-carrying hemoglobin in red blood cells. The iron levels are low, the transferrin saturation is high, and the ferritin level is low.
- Rheumatoid arthritis. This form of arthritis inflames the membranes or tissues lining the joints.
- Overuse of iron supplements.
- Kidney failure.
- Severe infection.
Current as of: December 27, 2021
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Martin J. Gabica MD - Family Medicine
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