Iron is an essential trace element—primarily derived from dietary sources—that is necessary for the formation of red blood cells. Iron deficiency will lead to anemia (low levels of red blood cells), while persistently high levels can be toxic to the body’s organs. The following blood tests are used to measure iron levels in the blood, the amount of iron stored in the body, and the body’s capacity to absorb iron.
Ferritin—the major iron-storage protein—is measured to determine the amount of iron stored in the body.
Iron level is determined by measuring the quantity of iron bound to the protein transferrin. Transferrin, which is formed in the liver, is the major carrier of iron in the bloodstream.
Total iron-binding capacity (TIBC) measures all of the proteins available for transporting iron; since transferrin is the primary carrier, this test indirectly measures transferrin levels.
Transferrin saturation—which is determined by dividing TIBC into the blood iron level—is the percentage of transferrin that is saturated with iron. If less than 20% of transferrin is iron-saturated, delivery of iron to developing red cells is impaired; if greater than 60% is saturated, iron may be deposited in organs other than the bone marrow, causing organ damage.
Purpose of the Iron Tests
- To detect or evaluate abnormalities of iron metabolism
- To determine the cause of anemia and to monitor patients with chronic anemia
- To detect or evaluate iron overload (hemochromatosis is the most common iron overload disease), and to monitor iron removal in people with hemochromatosis
Who Performs Iron Tests
- A nurse or a technician will draw the blood sample.
Special Concerns about Iron Tests
- Taking iron supplements can affect the results of these tests.
- A nuclear medicine scan performed within the last 4 days may affect the results, because blood samples may be analyzed with a laboratory technique that also utilizes a radioactive isotope (radioimmunoassay).
- Blood samples should be taken early in the morning for the iron level test, since iron levels vary throughout the day.
- While no fasting is required before a ferritin test, recent ingestion of a meal containing a high iron content (from red meat, for example) can cause elevated levels.
Before the Iron Tests
- Tell your doctor if you have had any recent procedures, such as a nuclear scan, that introduce radioactive material into your bloodstream, or if you have had a recent blood transfusion.
- Inform your doctor of any medications, herbs, or supplements that you regularly take.
- Do not eat or drink anything for 8 hours before a blood test for iron level, TIBC, or transferrin. No fasting is necessary before a test for ferritin levels.
- Do not take iron pills for 24 hours before the test.
What You Experience
- A sample of your blood is drawn from a vein in your arm and sent to a laboratory for analysis.
Risks and Complications of Iron Tests
After the Iron Tests
- Immediately after blood is drawn, pressure is applied (with cotton or gauze) to the puncture site.
- You may return home and resume your normal activities.
- Blood may collect and clot under the skin (hematoma) at the puncture site; this is harmless and will resolve on its own. For a large hematoma that causes swelling and discomfort, apply ice initially; after 24 hours, use warm, moist compresses to help dissolve the clotted blood.
Results of Iron Tests
- Your blood sample is sent to a laboratory for analysis. A doctor will review the results for evidence of iron deficiency, iron overload, or another problem. Abnormal results on iron tests can be caused by many conditions (including bleeding, malnutrition, malabsorption, excessive iron absorption, different types of anemia, liver disease, cancer, infection, and inflammation), as well as by blood transfusions.
- If an abnormality is found and the doctor can make a definitive diagnosis, appropriate treatment will begin.
- In many cases, abnormal results on one or more iron tests will necessitate additional tests to pinpoint the cause of the problem.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media