RBC copper 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 RBC copper:

  • Optimal 53 – 91 μg/dL (0.53 – 0.91 mg/L); out of range below 53 or above 91 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

UnitOptimalSufficientOut of range
μg/dL53 – 91—below 53 or above 91
mg/L0.53 – 0.91—below 0.53 or above 0.91
μmol/L8.3 – 14.3—below 8.3 or above 14.3

No separate Sufficient band is currently defined for this marker.

What the evidence says

The band is Quest's interval, 53 to 91 μg/dL (0.53 to 0.91 mg/L). NMS Labs, which runs the test for Mayo, agrees on the upper edge of 91 but starts at 59, so a result of 53 to 58 would be low there. The μmol/L row is a conversion: no UK or European laboratory interval was found, and the test is rarely ordered outside the US. No source supports a narrower optimal range. Read it with serum copper, ceruloplasmin and zinc.

Assay: Results differ meaningfully between platforms and methods. Compare against the interval printed by the issuing laboratory before acting on a borderline value.

Sources

  • Copper, RBC (test code 3481) — Quest Diagnostics, 2026 · Laboratory / reference-interval sourceRBC copper by ICP-MS: 0.53 to 0.91 mg/L (53 to 91 μg/dL). Both of Sera's edges.
  • Copper, RBCs (Test Code FCOPP) — NMS Labs (performing laboratory), Bronson Laboratory Services catalog, 2026 · Laboratory / reference-interval source2.5th to 97.5th percentiles 59 to 91 μg/dL (n = 1999). Confirms the upper edge; its lower edge is 59 rather than 53.

What Copper (RBC) measures

Copper measured inside red blood cells rather than in serum.

Reflects copper stores over the life of the red cells, so it moves more slowly than serum copper and is less affected by inflammation. Read it with serum copper, ceruloplasmin and zinc: high zinc intake lowers copper, and low copper can cause anaemia and low white cells.

Related vitamins & minerals markers

See RBC copper in the full list of biomarker ranges

About the author

Alina Radu is the founder of Sera and a software engineer. The idea started with her own Hashimoto's tests, scattered across years without the big picture. She is not a clinician: these ranges are compiled from the published sources linked on each page, with every source named. Alina Radu on LinkedIn

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.