Beta-2 Microglobulin 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 Beta-2 Microglobulin:

  • Optimal 0.8 – 2.4 mg/L (0.8 – 2.4 μg/mL); sufficient 0.6 – 2.7 mg/L (0.6 – 2.7 μg/mL); out of range above 2.7 mg/L.

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
mg/L0.8 – 2.40.6 – 2.7above 2.7
μg/mL0.8 – 2.40.6 – 2.7above 2.7

Bounded on the high side only — a low result is not treated as out of range. No source gives a low beta-2 microglobulin a clinical meaning, and laboratory lower limits differ twofold (0.6 against 1.21).

What the evidence says

Answers two different questions with one number. Filtered freely and reabsorbed proximally, so it tracks filtration much as cystatin C does; it also rises with cell turnover, which is where its prognostic weight in myeloma and lymphoma comes from. A raised value needs the clinical context before it means kidney disease. The bands are laboratory reference limits and differ by method: Labcorp's adult interval ends at 2.4 mg/L and Mayo Clinic Laboratories' at 2.7. A low result has no published meaning and is not flagged.

Sources

  • β2-Microglobulin — Labcorp, 2026 · Laboratory / reference-interval sourceAdult (over 18) serum reference interval 0.6 to 2.4 mg/L in both sexes. Matches Sera's optimal upper edge of 2.4 and acceptable lower edge of 0.6.
  • B2M - Overview: Beta-2-Microglobulin, Serum — Mayo Clinic Laboratories, 2026 · Laboratory / reference-interval sourceReference values 1.21 to 2.70 mcg/mL by nephelometry; below 4 mcg/mL is a good prognostic factor in multiple myeloma. 2.7 is the highest published upper limit found and is the proposed acceptable upper edge.

What Beta-2 Microglobulin measures

A small protein shed from the surface of nucleated cells, filtered by the glomerulus and reabsorbed by the tubule.

Reads two different things depending on the question. Filtered freely and reabsorbed proximally, so a raised blood level tracks reduced filtration much as cystatin C does; it also rises with cell turnover, which is why it carries prognostic weight in myeloma and lymphoma. A raised value therefore needs the clinical context before it means kidney disease.

Related kidney & electrolytes markers

See Beta-2 Microglobulin 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.