TIBC stands for total iron binding capacity. It measures how much room is available for binding iron in the blood. It primarily reflects transferrin, the most abundant iron-carrying protein in circulation.
TIBC will increase with iron deficiency as it attempts to create more room for carrying iron in the face of insufficiency. However, levels may not change until iron has become significantly depleted. TIBC can also be elevated with pregnancy and polycythemia vera, as well as with oral contraceptives and fluorides.
TIBC will decrease in the event of too much iron or iron overload and can decrease with the use of chloramphenicol and ACTH. It will also decrease with liver disease as the liver is needed for the production of serum transferrin. Therefore, TIBC may not be considered a direct measurement of iron metabolism in liver disease.
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