UIBC optimal range and reference range

Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026

Sera's bands for UIBC:

Optimal 112 – 347 μg/dL (20 – 62 μmol/L); out of range below 112 or above 347 μg/dL.

Evidence grade: Published reference interval. A band that primarily reflects a published adult laboratory or population reference interval. It is not necessarily applicable to every assay or laboratory.

All units

Unit	Optimal	Sufficient	Out of range
μg/dL	112 – 347	—	below 112 or above 347
μmol/L	20 – 62	—	below 20 or above 62

No separate Sufficient band is currently defined for this marker.

What the evidence says

UIBC is the part of transferrin's iron-carrying capacity that is still empty; it rises in iron deficiency and falls in iron overload and inflammation. The band, 112 to 347 µg/dL, sits within a few micrograms of the interval commonly used by US laboratories, 111 to 343. It is method-dependent, so the range printed on the client's report takes precedence. There is no guideline threshold and no evidence for a narrower optimal band; transferrin saturation and ferritin carry the clinical thresholds.

Sources

Population Heterogeneity in Iron Biomarkers by Age, Sex, Menopausal Status, and Race in Healthy U.S. Adults: A Cross-Sectional Analysis from the All of Us Research Program — Zeidan RS, Yang JJ, He R, et al. — Nutrients, 2026 · Peer-reviewed publicationLists the reference intervals commonly used by US clinical laboratories, according to the National Board of Medical Examiners: UIBC 111 to 343 µg/dL in men and women of all ages. Within a few units of Sera's 112 to 347.

What UIBC (Unsaturated Iron Binding Capacity) measures

The share of your blood's iron-carrying capacity that is still empty. TIBC minus the iron already being carried.

Mostly a working number rather than a result: most analysers measure iron and UIBC and then calculate TIBC from the two, which is why European and Gulf reports often print this where UK and US reports print TIBC. What matters clinically is transferrin saturation and TIBC. Serum iron swings a lot through the day, so UIBC does too, and a trend built from samples drawn at different times is largely noise.

Related blood cell health markers

See UIBC in the full list of biomarker ranges

This page is a reference for practitioners, not medical advice. Sera's bands are practitioner targets for structured review, not diagnostic thresholds, and Sera does not diagnose or recommend treatment. Read a result alongside the interval printed by the issuing laboratory and the client's history and symptoms. Range set: Sera Production, version 1.0, last reviewed November 9, 2026.