One.
One.

Platform

Company

Resources

Create Account

One Health helps you track and understand your health simply.

Create Account

One Health helps you track and understand your health simply.

Immunoglobulin M (IgM)

Microbiology & Infection

IgMImmunoglobulin M

Review status

Currently under review

Pending specialist review and validation.

What it shows

IgM is one of the major antibody types your immune system makes. It is often the first antibody produced when you encounter a new infection, and it helps your body contain germs while longer-lasting antibodies are forming. A blood test can measure the amount of IgM circulating in your bloodstream.

Clinicians may order a total IgM test to assess your overall immune function or to look for conditions that affect antibody production. The test is different from pathogen-specific IgM tests, which look for IgM directed against a particular virus or bacterium.

Why it matters

Measuring IgM can help evaluate how your immune system is responding to illness and whether you may have an immune deficiency or an overproduction of a single antibody type. Doctors may order this test if you have frequent or unusual infections, unexplained inflammation, enlarged lymph nodes, or signs of a plasma cell or lymphoid disorder. It can also be part of a broader workup when liver disease, autoimmune conditions, or protein loss are suspected.

Results can guide follow-up testing, such as checking other immunoglobulins, looking for a monoclonal protein, or ordering pathogen-specific antibody tests. Understanding your IgM level in context with your symptoms, exam, and other labs helps determine whether treatment or monitoring is needed.

Understanding your results

A higher IgM level can be seen during early immune responses to infections, with some autoimmune or inflammatory diseases, or when a single clone of cells produces excess IgM. Liver conditions and certain chronic infections may also raise IgM. A lower level can occur with some inherited or acquired immune deficiencies, after certain therapies that reduce antibody-producing cells, or with significant protein loss.

Your report may show IgM as a concentration or as activity units, depending on the method used. Laboratories also set age and sex specific reference intervals. If your result is outside the reference interval, your clinician will consider your symptoms, medications, and other test results before deciding on next steps. Sometimes repeating the test, checking other immunoglobulins, or ordering more specific antibody or protein studies is appropriate.

Reference ranges

0 – 0.15 g/L
Female
0 days – 1 month
0 – 0.15 g/L
Male
0 days – 1 month
0 – 11 U/mL
All sexes
0 days – 150 years
0.15 – 0.57 g/L
Female
1 month – 2 months
0.11 – 0.45 g/L
Male
1 month – 2 months
0.19 – 0.76 g/L
Female
2 months – 3 months
0.15 – 0.6 g/L
Male
2 months – 3 months
0.22 – 0.91 g/L
Female
3 months – 4 months
0.17 – 0.71 g/L
Male
3 months – 4 months
0.24 – 1.01 g/L
Female
4 months – 5 months
0.19 – 0.78 g/L
Male
4 months – 5 months
0.26 – 1.05 g/L
Female
5 months – 6 months
0.2 – 0.82 g/L
Male
5 months – 6 months
0.27 – 1.1 g/L
Female
6 months – 7 months
0.21 – 0.86 g/L
Male
6 months – 7 months
0.29 – 1.15 g/L
Female
7 months – 8 months
0.22 – 0.9 g/L
Male
7 months – 8 months
0.3 – 1.19 g/L
Female
8 months – 9 months
0.23 – 0.94 g/L
Male
8 months – 9 months
0.31 – 1.24 g/L
Female
9 months – 10 months
0.24 – 0.97 g/L
Male
9 months – 10 months
0.31 – 1.29 g/L
Female
10 months – 11 months
0.24 – 1.01 g/L
Male
10 months – 11 months
0.33 – 1.34 g/L
Female
11 months – 1 year
0.26 – 1.05 g/L
Male
11 months – 1 year
0.34 – 1.34 g/L
Female
1 year – 2 years
0.26 – 1.05 g/L
Male
1 year – 2 years
0.41 – 1.58 g/L
Female
2 years – 3 years
0.32 – 1.23 g/L
Male
2 years – 3 years
0.44 – 1.72 g/L
Female
3 years – 4 years
0.34 – 1.35 g/L
Male
3 years – 4 years
0.45 – 1.72 g/L
Female
4 years – 5 years
0.36 – 1.35 g/L
Male
4 years – 5 years
0.46 – 1.72 g/L
Female
5 years – 9 years
0.36 – 1.35 g/L
Male
5 years – 9 years
0.46 – 1.73 g/L
Female
9 years – 10 years
0.36 – 1.36 g/L
Male
9 years – 10 years
0.46 – 1.74 g/L
Female
10 years – 11 years
0.36 – 1.38 g/L
Male
10 years – 11 years
0.46 – 1.77 g/L
Female
11 years – 12 years
0.36 – 1.4 g/L
Male
11 years – 12 years
0.46 – 1.79 g/L
Female
12 years – 13 years
0.36 – 1.42 g/L
Male
12 years – 13 years
0.47 – 1.82 g/L
Female
13 years – 14 years
0.36 – 1.45 g/L
Male
13 years – 14 years
0.48 – 1.86 g/L
Female
14 years – 15 years
0.38 – 1.49 g/L
Male
14 years – 15 years
0.48 – 1.91 g/L
Female
15 years – 16 years
0.38 – 1.56 g/L
Male
15 years – 16 years
0.44 – 1.68 g/L
Female
16 years – 18 years
0.36 – 1.49 g/L
Male
16 years – 18 years
0.5 – 3 g/L
Female
18 years – 150 years
0.5 – 3 g/L
Male
18 years – 150 years

Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.

Factors that could impact Immunoglobulin M (IgM)

  • Recent or ongoing infection

    IgM often rises early in an infection, so testing soon after symptoms start can show a transient increase. As the illness resolves and IgG develops, IgM may decline.

  • Immunosuppressive therapies

    Medicines that affect B cells or antibody production, such as rituximab, chemotherapy, or high-dose steroids, can lower IgM for weeks to months.

  • Protein loss and liver function

    Kidney disease with protein loss, intestinal protein loss, or severe liver disease can alter immunoglobulin levels and may lower or sometimes raise IgM.

  • Monoclonal gammopathy

    Conditions such as Waldenström macroglobulinemia or IgM MGUS can produce excess IgM from a single clone of cells and affect total IgM results.

  • Age and biological sex

    Normal IgM levels vary by age and sex, especially in infancy and childhood. Your lab interprets results using reference intervals tailored to these factors.

  • Specimen quality and timing

    Hemolysis, lipemia, or improper handling can interfere with some assays. Consistent collection timing and proper processing help ensure reliable results.

  • Immunoglobulin replacement

    Infusions containing pooled antibodies rarely include significant IgM, but they can influence interpretation of overall immune testing and related studies.

  • Autoantibodies and assay interference

    Some autoantibodies or rheumatoid factor can interfere with certain immunoassays. If results do not fit the clinical picture, method-specific confirmation may help.

2026

References

  1. McGill University Health Centre. (2009, October 05). IgM (Task CD 684751). Laboratory reference ranges.
  2. McGill University Health Centre. (2016, October 20). IgM (Task CD 691233). Laboratory reference ranges.
  3. Bonilla, F. A., Khan, D. A., Ballas, Z. K., Chinen, J., Frank, M. M., Hsu, J. T., Pérez, E. E., & Routes, J. M. (2015). Practice parameter for the diagnosis and management of primary immunodeficiency. Journal of Allergy and Clinical Immunology, 136(5), 1186–1205.e1–78.
  4. Ward, C., & Bonilla, F. A. (2019). Immunoglobulin disorders and their management. The Journal of Allergy and Clinical Immunology: In Practice, 7(2), 594–604.