Immunoglobulin M
Other marker
IgM
Immunoglobulin M
The first antibody class produced in response to a new infection. A raised IgM points to recent or acute exposure, while a low IgM suggests impaired antibody production.
PED Notes
Measured alongside IgG and IgA as part of an immunoglobulin panel. AAS-driven immunosuppression can lower IgM along with the other classes, and the pattern across all three is more informative than any single value. A raised IgM most often reflects a recent infection rather than anything related to compound use. Persistently elevated IgM with a normal IgG deserves specialist assessment because it can indicate a specific antibody disorder.
When high
High IgM:
- Consider recent or ongoing infection -- IgM rises first in an acute response and falls as IgG takes over; repeat in 4-6 weeks to confirm it is settling
- Serum protein electrophoresis with immunofixation -- a monoclonal IgM band raises the possibility of Waldenstrom macroglobulinaemia and needs haematology referral
- Liver screen -- primary biliary cholangitis characteristically raises IgM
- Reduce alcohol -- an independent contributor to raised immunoglobulins
A persistently raised IgM that does not settle after a presumed infection requires specialist review.
When low
Low IgM:
- Repeat with the full panel (IgG, IgA, IgM) -- an isolated low IgM is often benign, while a pan-low pattern indicates a broader antibody deficiency
- Review AAS dose and duration -- supraphysiological androgen exposure suppresses antibody production
- Review immunosuppressive medications -- corticosteroids and B-cell-depleting therapies are common causes
- Support with adequate protein, zinc, and vitamin D repletion as for low IgG
Selective IgM deficiency is uncommon and warrants immunology referral when paired with recurrent infections.
History Chart
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Frequently Asked Questions
Reference Ranges
Standard Range
VitalMetrics Range