TIBC

What it is

TIBC (total iron-binding capacity) estimates the total carrying capacity of transferrin, the protein that ferries iron around your bloodstream — think of it as counting the seats on the bus rather than the passengers. Because it largely tracks transferrin levels, it can shift with nutrition, liver function, pregnancy, estrogen, and inflammation for reasons that have nothing to do with iron itself. It exists mainly to be combined with serum iron (which is how transferrin saturation is calculated) and is read alongside ferritin rather than interpreted on its own.

Typical range

Reference ranges vary between laboratories, and what is normal for you depends on your own history. Your own lab’s range is the one printed on your report.

Worth asking your clinician

• What does my TIBC add when read together with my serum iron and ferritin?
• Could anything else going on with my health be shifting this number independently of my iron?
• Is the overall pattern across my iron panel something you'd want to look at again later?