IgM 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 IgM:

  • Optimal 50 – 200 mg/dL (0.5 – 2 g/L); sufficient 40 – 230 mg/dL (0.4 – 2.3 g/L); out of range below 40 or above 230 mg/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
mg/dL50 – 20040 – 230below 40 or above 230
g/L0.5 – 20.4 – 2.3below 0.4 or above 2.3

What the evidence says

Points at a recent rather than an established response. A markedly high IgM with a low IgG suggests a class-switching defect, and a persistently raised IgM in an older adult warrants a paraprotein screen. The bands are adult laboratory reference intervals: 0.4 to 2.3 g/L is the interval used by several NHS laboratories, and 0.5 to 2 g/L is a narrower one used by others. Some laboratories run wider, up to 2.5 g/L or 263 mg/dL, so use the interval printed on the report where it differs.

Sources

  • Immunoglobulins and Electrophoresis — Gloucestershire Hospitals NHS Foundation Trust, Pathology, 2025 · Laboratory / reference-interval sourceAdult (16 to 60 years) IgM range 0.40 to 2.30 g/L, the same as Sera's sufficient band. Page updated September 2025.
  • Immunoglobulins — York and Scarborough Teaching Hospitals NHS Foundation Trust, Laboratory Medicine, 2026 · Laboratory / reference-interval sourceIgM 0.5 to 1.9 g/L from 6 to 45 years and 0.5 to 2.0 g/L over 45; adult IgG 6 to 16 g/L. The over-45 IgM interval is Sera's optimal band. Test directory page as opened in October 2026; it carries no date.
  • Immunoglobulins (IgA, IgG, IgM), Quantitative — ARUP Laboratories, 2026 · Laboratory / reference-interval sourceReference intervals at 19 years and older: IgG 768 to 1632 mg/dL, IgA 68 to 408, IgM 35 to 263. The IgM interval is a little wider than Sera's 40 to 230 mg/dL on both sides. Test directory page as opened in October 2026.

What Immunoglobulin M (IgM) measures

The first antibody class produced in a new immune response, and the largest of them.

A raised IgM points at a recent or ongoing response rather than an established one. A markedly high level with a low IgG suggests a class-switching defect, and a persistently raised IgM in an older adult warrants a paraprotein screen.

Related autoimmune markers

See IgM 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.