Spare iron capacity Unbound Iron Binding Capacity (UIBC)
The room still spare on your iron carriers.
Also printed asUnsaturated Iron-Binding Capacity · UIBC · Unsaturated Iron Binding Capacity
What it measures
The seats on your iron transport that are currently empty - total capacity minus the iron in them.
Carries the same information as total capacity and saturation; labs report it because the three are calculated from one another.
Why it matters for how long you stay well
It adds nothing beyond total capacity and saturation, so use those and treat this as arithmetic.
How it shows up in daily life
It is the same story as binding capacity, just counted from the empty side rather than the full one.
High and low readings
When it reads high
Many empty seats, the iron-deficiency direction.
When it reads low
Few empty seats, the iron-replete or overload direction.
What moves it
Daily life
- iron stores
- long-running inflammation
Medicines known to shift it
- iron supplements (lower it as stores refill)
Listed so a result can be read in context. It is not advice to start, stop or change any medicine; that decision belongs with your physician.
Read it with
Markers that move this one, or that this one moves. One number read alone can mislead.
- Iron-binding capacityKnown mechanism
Iron-binding capacity moves with it
Spare capacity is total capacity minus the iron already loaded on. So the two move together, simply counted from opposite ends.
Common questions
What does Unbound Iron Binding Capacity measure?
The seats on your iron transport that are currently empty - total capacity minus the iron in them. Carries the same information as total capacity and saturation; labs report it because the three are calculated from one another.
What does a high Spare iron capacity result usually mean?
Many empty seats, the iron-deficiency direction.
What does a low Spare iron capacity result usually mean?
Few empty seats, the iron-replete or overload direction.
What is the usual reference range for Spare iron capacity?
A broad adult reference band is 120–370 µg/dL. Labs differ, so read your result against the band printed on your own report.
Educational only, not a diagnosis. A single number means little without your history and the rest of your panel, so discuss your own results with your physician.
Typical adult reference band
- Adults
- 120–370 µg/dL
Labs differ. The band printed on your own report is the one that applies to your result.
Reported in µg/dL
Ageing relevance
1/5
A general health marker with limited direct ageing data.
Worth knowing
It is simply the total capacity minus the iron already sitting on the carriers.
Have a report with this marker on it? Read it in context.
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