Total iron-binding capacity (TIBC) or sometimes transferrin iron-binding capacity is a medical laboratory test that measures the blood’s capacity to bind iron with transferrin.[1] It is performed by drawing blood and measuring the maximum amount of iron that it can carry, which indirectly measures transferrin[2] since transferrin is the most dynamic carrier.

Taken together with serum iron and percent transferrin saturation clinicians usually perform this test when they are concerned about anemia, iron deficiency or iron deficiency anemia. However, because the liver produces transferrin, alterations in function (such as cirrhosis, hepatitis, or liver failure) must be considered when performing this test. It can also be an indirect test of liver function, but is rarely used for this purpose.