At a Glance
Why Get Tested?
To learn about your body's iron stores
When to Get Tested?
When your doctor suspects you may have too much or too little iron in your body because of a variety of conditions
Sample Required?
A blood sample taken from a vein in your arm
The Test Sample
What is being tested?
TIBC measures the total capacity of your blood to transport iron, and therefore reflects your body's iron stores. TIBC correlates with the amount of the protein transferrin in your blood. Transferrin is a protein that attaches iron molecules and transports iron to the blood plasma. Transferrin is largely made in the liver and regulates your body’s iron absorption into the blood. While the two tests (TIBC and transferrin) are different, they measure essentially the same thing. Most laboratories only measure one or the other. A few laboratories are now measuring the number of sites on transferrin that are not already carrying iron; this is referred to as unsaturated iron binding capacity (UIBC). This number can be added to the serum iron to calculate the TIBC.
How is the sample collected for testing?
A blood sample is taken 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.
The Test
How is it used?
TIBC (or transferrin) is typically used along with iron and ferritin to evaluate people suspected of having too much or too little iron. Usually, about one third of the transferrin measured is being used to transport iron. In iron deficiency, iron is low, but TIBC is increased. In iron overload, such as in haemochromatosis, iron will be high and TIBC will be low or normal.
Because transferrin is made in the liver, TIBC and transferrin will also be low with liver disease.
When is it requested?
TIBC (or transferrin) measurements may be requested when it appears that you have too much or too little iron in your system. If you have anaemia, especially if the red cells are small and pale (microcytic and hypochromic), this may be due to iron deficiency and iron tests are usually performed. If your doctor suspects you may have too much iron, or if you have a family history of haemochromatosis, iron and TIBC (or transferrin or UIBC) may be used to see if further testing is needed.
What does the test result mean?
High TIBC usually indicates iron deficiency. A low TIBC may occur if you have haemochromatosis (too much stored iron), anaemia caused by infections and chronic diseases, malnutrition, cirrhosis, or nephrotic syndrome (a kidney disease that causes loss of protein in urine).
Is there anything else I should know?
Taking the oral contraceptive pill can result in a higher TIBC result.
Taking chloramphenicol can decrease TIBC levels. Some laboratories routine only use studies of the red cells (FBC) and ferritin to investigate anaemia and monitor treatment.
Common Questions
Ask a Laboratory Scientist
Article Sources
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.
