Total Iron-Binding Capacity
Also written as: TIBC
How much iron the blood's carrier protein, transferrin, could hold in total.
What it measures
The total capacity of the blood to carry iron. Iron travels attached to a protein called transferrin, and TIBC estimates how much iron all the transferrin in the sample could hold if it were fully loaded.
Why a doctor orders it
Ordered alongside serum iron and ferritin to help work out why iron results are abnormal. The pattern across the whole iron panel is more informative than any single value.
What is generally associated with a higher result
Broadly associated with iron deficiency, because the body makes more transferrin when iron is scarce. It can also rise in pregnancy and with estrogen-containing medicines such as the contraceptive pill.
What is generally associated with a lower result
Broadly associated with inflammation, chronic illness, liver conditions, and iron overload states, because transferrin production falls in those settings.
Everyday things that move this number
Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:
- Pregnancy
- Oral contraceptives and other estrogen-containing medicines
- Recent illness or inflammation
- Overall nutritional state, since transferrin is a protein made by the liver
Questions to take to your appointment
- How does this fit with the ferritin and serum iron results from the same draw?
- Could a medicine I take, such as the contraceptive pill, be influencing it?
- Is transferrin saturation the more useful figure to look at here?
Build a printable questionnaire with your own results →
Where to read more
MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .
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