Total iron-binding capacity, TIBC, transferrin saturation
This test measures the amount of the protein transferrin in your blood.
Your liver makes transferrin. When your body's stores of iron run low, your liver produces more transferrin to get more iron into your blood.
Iron plays many important roles in your body, including helping your red blood cells carry oxygen to the cells in your body. 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 healthcare provider more information about health issues like anemia that are affecting your body's iron supply.
You may need this test if your healthcare provider 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. Hemoglobin is the substance that helps your red blood cells carry oxygen.
Symptoms of anemia can include:
Extreme tiredness or weakness
Pale skin color
Shortness of breath and fast heartbeat during physical activity
Less common symptoms include abnormal cravings or brittle nails.
Anemia usually happens 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.
Your healthcare provider 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
Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you.
Results are given in milligrams per deciliter (mg/dL). The normal range for transferrin is 204 to 360 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 250 to 450 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 15% to 50%. In severe cases of iron-deficiency and anemia, this number may fall below 10%.
Many other medical conditions can cause high or low levels of transferrin. The results of these tests, and other tests, can help your healthcare provider determine the cause of your symptoms.
The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand.
Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore.
Aspirin, antibiotics, and birth control pills can affect your results.
You don't need to prepare for this test. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.