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.
Why It Is Done
A test for iron is done to:
How To Prepare
Do not take iron supplements for 12 hours before having an iron test.
Iron levels change throughout the day so it is best to do iron tests in the morning, when iron levels are highest.
How It Is Done
The health professional drawing blood will:
- Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
- Clean the needle site with alcohol.
- Put the needle into the vein. More than one needle stick may be needed.
- Attach a tube to the needle to fill it with blood.
- Remove the band from your arm when enough blood is collected.
- Put a gauze pad or cotton ball over the needle site as the needle is removed.
- Put pressure to the site and then a bandage.
How It Feels
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of a problem from having a blood sample taken from a vein.
- You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
- In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
- Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.
An iron test checks the amount of iron in the blood to see how well iron is metabolized in the body.
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Total iron-binding capacity (TIBC)
| Men and women:|
250–450 mcg/dL or 45–76 mcmol/L
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 whether a high amount of iron is due to 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.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- Taking medicines, such as chloramphenicol (Chloromycetin), birth control pills, corticotropin, estrogen, aspirin, and iron supplements.
- Using herbal remedies, especially St. John's wort and saw palmetto.
- Taking vitamin B12 supplements in the 48 hours before the iron test.
- Not getting enough sleep (sleep deprivation).
- Being under a lot of stress.
- Having a blood transfusion in the past 4 months.
What To Think About
- Taking iron supplements for tiredness can mask an iron problem. Talk to your doctor about taking iron supplements.
- Iron levels change during the day. Iron tests are best done in the morning, when iron levels are highest.
- The results of an iron test are also checked with results of a complete blood count (CBC), ferritin, and transferrin tests. The ferritin test is often better than an iron test to see if iron deficiency is present. An iron test and ferritin test are often done at the same time. For more information, see the topics Complete Blood Count (CBC) and Ferritin.
- A test called the siderocyte stain test checks the number of red blood cells that have particles of iron not bound to hemoglobin (siderocytes). Normally, very low numbers of siderocytes are present in blood. High levels of siderocytes in adults may mean a type of anemia, iron overload, lead poisoning, hemochromatosis, or a severe infection is present.
- When iron deficiency anemia is diagnosed, the source of the anemia must be found and treated. Iron deficiency can be caused by long-term (chronic) blood loss from heavy menstrual bleeding, pregnancy, not enough iron in the diet, or bleeding inside the intestinal tract (from ulcers, colon polyps, colon cancer, hemorrhoids, or other conditions). In rare cases, too much iron may be lost through the skin (because of a disease such as psoriasis) or in the urine. Iron deficiency anemia can be easily treated with iron supplements, but the key is to identify it and stop the iron loss.
- Hemochromatosis can be treated with medicines to help the body get rid of extra iron. A procedure called a phlebotomy can also be done to remove iron from the body.
Other Works Consulted
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
|Primary Medical Reviewer||E. Gregory Thompson, MD - Internal Medicine|
|Specialist Medical Reviewer||Joseph O'Donnell, MD - Hematology, Oncology|
|Last Revised||August 3, 2010|