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Does this test have other names?

Total iron-binding capacity, TIBC, transferrin saturation

What is this test?

This test measures the amount of the protein transferrin in your blood.

Your liver makes transferrin. It creates much more when your body's stores of iron run low.

Iron plays many important roles in your body, including helping your red blood cells carry oxygen. Nearly all the iron in your body is normally attached to transferrin.

Normally, your body carefully monitors your iron level and tries to keep it from rising too high or falling too low.

This test can give your health care provider more information about health issues like anemia that are affecting your body's iron supply.

Why do I need this test?

You might need this test if your doctor suspects that you have a certain type of anemia. In general, anemia means you have a low number of red blood cells. One type of anemia is iron deficiency anemia. If you have this type, you don't have enough iron to properly make hemoglobin, the substance that helps your red blood cells carry oxygen.

Symptoms of anemia can include:

  • Extreme tiredness

  • Irritability

  • Headaches

  • Shortness of breath and fast heartbeat during physical activity

Anemia usually occurs because of blood loss or because you aren't absorbing enough iron from your food. Pregnant women are also at higher risk of developing this problem.

What other tests might I have along with this test?

Your doctor may also order other tests, including:

  • Complete blood count, or CBC

  • Tests to measure how much iron is in your blood

  • Measurement of ferritin, a protein that holds most of your body's iron reserves

  • Stool tests

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

Results are given in milligrams per deciliter (mg/dL). The normal range for transferrin is 170 to 370 mg/dl. If you have a higher amount, you may have iron-deficiency anemia. If you have a lower level, you may have another problem, such as liver disease and hemolytic anemia.

Transferrin may also be measured using a value called total iron-binding capacity (TIBC). Results are given in micrograms per deciliter (mcg/dL). Normal values are 300 to 360 mcg/dL. A higher level means that you may have iron-deficiency anemia.

Another measurement, called transferrin saturation, checks how many places on your transferrin that can hold iron are actually doing so. Normal values are 20 to 50 percent. In severe cases of iron deficiency and anemia, this number may fall below 10 percent.

Many other medical conditions can cause high or low levels of transferrin.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

Oral contraceptives can affect your results.

How do I get ready for this test?

You don't need to prepare for this test. But be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.