Iron (Fe)
Test OverviewAn 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 DoneA test for iron is done to: How To PrepareDo 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 DoneThe 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 on the site and then put on a bandage.
How It FeelsThe 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. RisksThere 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.
ResultsAn iron test checks the amount of iron in
the blood to see how well iron is
metabolized in the body. NormalThe 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)footnote 1| Men and
women: | 250-450 mcg/dL
or 45-76 mcmol/L |
|---|
Transferrin saturationfootnote 1| Men: | 10%-50% |
|---|
| Women: | 15%-50% |
|---|
High and low valuesThe 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.
- Bleeding.
- 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 birth control pills, corticotropin, estrogen, aspirin, and
iron supplements.
- Using some herbal remedies, especially St. John's wort
and saw palmetto.
- Taking vitamin B12 supplements in the 48 hours
before the iron test.
- 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 before 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.
- 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 that 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.
ReferencesCitations- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
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.
CreditsByHealthwise Staff
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Adam Husney, MD - Family Medicine
Specialist Medical ReviewerMartin J. Gabica, MD - Family Medicine Current as ofApril 3, 2017 Current as of:
April 3, 2017 Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins. Last modified on: 8 September 2017
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