At a Glance
Why Get Tested?
To determine your blood iron level
When to Get Tested?
When your doctor suspects that you may have too little or too much iron in your body
A blood sample drawn from a vein in your arm
Test Preparation Needed?
You may be instructed to fast for 12 hours before sample collection; in this case, only water is permitted.
The Test Sample
What is being tested?
The serum iron test measures the amount of iron in the liquid portion of blood. Iron is an essential trace element that is absorbed from food and transported throughout the body by transferrin, a protein produced by the liver. Iron is necessary for the production of healthy red blood cells (RBCs). It is an important part of hemoglobin, the protein in RBCs that enables them to carry oxygen throughout your body. Iron is also used in the production of some proteins, including myoglobin and some enzymes.
Normally, about 70% of the iron absorbed is incorporated into the hemoglobin inside RBCs. Most of the rest is stored in the tissues as ferritin or hemosiderin. If not enough iron is taken in from the diet, then levels in the blood may drop, which then can deplete iron stored in the body. Over time, low blood levels and decreased iron stores can lead to iron deficiency anemia. On the other hand, absorption of too much iron can lead to progressive accumulation and damage to organs such as the liver, heart, and pancreas.
The serum iron test measures the amount of iron that is in transit in the body – the iron that is bound to transferrin. The amount of iron present in the blood will vary throughout the day and from day to day. For this reason, serum iron is almost always measured with other iron tests, such as the total iron-binding capacity (TIBC), from which the transferrin saturation can be calculated. Transferrin saturation reflects the amount of iron being transported in the blood and its capacity to carry more. The use of several iron tests provides a more reliable measure of iron deficiency and iron overload than measuring serum iron by itself.
How is the sample collected for testing?
A blood sample is drawn by needle from a vein in your arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
Morning samples are preferred. You may be instructed to fast for twelve hours before sample collection. In this case, only water is permitted.
Ask a Laboratory Scientist
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 574-577.
Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 407-408.
Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 634-635.
(Modified 2009 March 13). About Iron. Iron Disorders Institute [On-line information]. Available online at http://www.irondisorders.org/Disorders/about.asp through http://www.irondisorders.org. Accessed June 2009.
(Updated 2007 August 24). Dietary Supplement Fact Sheet: Iron. NIH Office of Dietary Supplements [On-line information]. Available online at http://ods.od.nih.gov/factsheets/iron.asp through http://ods.od.nih.gov. Accessed June 2009.
Rathz, D. et. al. (Updated 2009 February 02). Toxicity, Iron. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/166933-overview through http://emedicine.medscape.com. Accessed June 2009.
Chen, Y. (Updated 2009 April 05). Iron Deficiency Anemia. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000584.htm. Accessed June 2009.
Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson RA and Pincus MR, eds. Philadelphia: 2007, Pg. 506-507.
(November 1, 2007) Centers for Disease Control and Prevention. Hemochromatosis, Biochemical testing. Available online at http://www.cdc.gov/ncbddd/hemochromatosis/training/diagnostic_testing/biochemical_testing.htm through http://www.cdc.gov. Accessed October 2009.
Iron Disorders Institute. Iron Tests. PDF available for download at http://www.irondisorders.org/Forms/irontests.pdf through http://www.irondisorders.org. Accessed October 2009.
Sources Used in Previous Reviews
Corbett, JV. Laboratory Tests & Diagnostic Procedures with Nursing Diagnoses, 4th ed. Stamford, Conn.: Appleton & Lang, 1996. Pp. 34-35, 41-43.
Frey, Rebecca J. Iron Tests. Chapter in: Gale Encyclopedia of Medicine, Edition One, 1999 Gale Research Group, Pg. 1648.
Witte DL, Crosby WH, Edwards CQ, Fairbanks VG, Mitros FA. Practice guideline development task force of the College of American Pathologists.
Boston University Medical Center: Community Outreach Health Information System. Available onlineat http://www.bu.edu/cohis/cardvasc/blood/anemia.htm#prevent through http://www.bu.edu.
Lyon, Elaine and Frank, Elizabeth L. Hereditary Hemochromatosis Since Discovery of the HFE Gene. Clinical Chemistry 47:1147-1156 (Jul 2001).