TOTAL IRON BINDING CAPACITY (TIBC)

TIBC (Total Iron Binding Capacity) is the maximum amount of iron that transferrin — the iron transport protein in your blood — could carry if it were fully saturated. The test works by adding excess iron to your serum, then measuring how much is bound. TIBC is therefore a surrogate for transferrin concentration.

Normally about one-third of transferrin is saturated with iron (transferrin saturation = 20–50%). In iron deficiency, the liver makes more transferrin (TIBC rises) but there is less iron to bind (so saturation falls). In anaemia of chronic disease, inflammation suppresses transferrin (TIBC falls) even though body iron may be adequate. In haemochromatosis (iron overload), transferrin is suppressed (low TIBC) and saturation is very high (>45%).

TIBC is one of the four components of an iron studies panel (Iron, TIBC, transferrin saturation, ferritin) used to evaluate iron-related anaemias. The pattern of these four together distinguishes iron deficiency from chronic disease — a clinically critical distinction because treatment differs (iron supplementation for one, treating the underlying disease for the other).

In Indian primary care, where iron deficiency anaemia affects more than half of all adult women, the iron studies panel is the first-line workup for any unexplained microcytic anaemia. A standalone TIBC has limited use; it is almost always interpreted with iron and saturation.

Fast for 8–10 hours. Avoid iron supplements for 24 hours before the test. Morning sample preferred (consistent with serum iron diurnal variation). Disclose oral iron, recent transfusion, infection, pregnancy, or oral contraceptive use.