Total iron binding capacity (TIBC) measures the maximum amount of iron that transferrin in the blood can carry. It is an indirect measure of transferrin concentration and reflects how much additional iron the blood could carry if transferrin were fully saturated with iron.

In iron deficiency, TIBC is elevated — the liver produces more transferrin, increasing the blood's capacity to bind any available iron. In iron overload or anaemia of chronic disease, TIBC is low or normal. TIBC is used alongside serum iron and transferrin saturation as part of a complete iron panel. Transferrin saturation (iron ÷ TIBC × 100) is the most useful derived value — low saturation indicates deficiency; high saturation indicates overload.