How to prepare
No fasting is required. No specific preparation is needed. Take medications as normal.
After the test
Share your result with your GP. Significantly elevated IgM warrants further investigation for conditions where lymphocytes, a type of white blood cell, multiply abnormally (lymphoproliferative conditions). Low IgM in the context of recurrent infections or known immunological risk factors should be assessed by an immunologist. As part of a complete immunoglobulin panel, IgM is interpreted alongside IgG and IgA. If you have visual disturbance, confusion or new neurological symptoms alongside a very high result, seek prompt medical attention rather than waiting for a routine appointment.
Your test results will be available in your private dashboard. If there are any urgent issues, we'll let you know so you can follow up with your health professional.
Understanding results
IgM is measured in grams per litre (g/L). Your result report includes the reference range that applies to your sample, and your practitioner can explain what your number means in your context.
- Elevated IgM: Common during acute or recent infections. Persistently high IgM can be seen in primary immunodeficiencies (such as hyper-IgM syndrome), chronic infections, and importantly in Waldenstrom's macroglobulinaemia where levels can be very high and cause increased blood viscosity.
- Low IgM: May indicate primary immunodeficiency, secondary immunodeficiency (from malignancy, medication, or immune-depleting diseases), or excessive loss of immunoglobulins.
- Isolated low IgM: Often an incidental finding with unclear significance in otherwise healthy adults.
