To learn about your body's iron stores
TIBC, UIBC and Transferrin
When your doctor suspects you may have too much or too little iron in your body because of a variety of conditions
A blood sample taken from a vein in your arm
You may be instructed to fast for 12 hours before the test; in this case, only water is allowed.
Total Iron Binding Capacity, or TIBC, measures the total capacity of your blood to bind and transport iron, and therefore reflects your body's iron stores. TIBC correlates with the amount of the protein transferrin in your blood, available to bind iron. Transferrin is a protein that attaches iron molecules and transports iron in 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 and 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 it used?
TIBC or transferrin are typically used along with iron and ferritin to evaluate people suspected of having too much or too little iron stored within their body. Usually, about one third of the transferrin measured is being used to transport iron, and this is called transferrin saturation. In iron deficiency, iron is low and fewer transferrin binding sites are used. This results in a low transferrin saturation, but an increased TIBC. In iron overload, such as in haemochromatosis, iron and transferrin saturation 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 or transferrin, or low transferrin saturation, usually indicates iron deficiency. A low TIBC or transferrin, or high transferrin saturation may occur if you have haemochromatosis (too much stored iron). Other causes of abnormal results include anaemia caused by infections and chronic diseases, malnutrition, cirrhosis, or nephrotic syndrome (a kidney disease that causes loss of protein in urine).
A summary of the changes in iron tests seen in various diseases of iron status is shown in the table below.
Disease Iron TIBC/Transferrin UIBC % Transferrin Saturation Ferritin Iron Deficiency Low High High Low Low Haemochromatosis High Low Low High High Chronic Illness Low Low Low/Normal Low Normal/High Iron Poisoning High Normal Low High Normal
Is there anything else I should know?
Does transferrin actually move iron around my body?
On This Site
Tests: Iron Tests, Serum Iron, Ferritin, Zinc Protoporphyrin, Full Blood Count, Haemoglobin, Haematocrit, Reticulocyte Count, Soluble Transferrin Receptor
Conditions: Anaemia, Haemochromatosis