Iron Bind.Cap. (TIBC): This test measures how well your blood can carry iron. Iron is important for making healthy red blood cells that carry oxygen around your body. TIBC stands for Total Iron-Binding Capacity—it checks how much iron your blood proteins (mainly one called transferrin) can hold. A high TIBC might mean you’re low in iron (iron deficiency), while a low TIBC might suggest your body has enough or too much iron, or problems with protein levels in your blood.