Home Biomarkers IgM Level

IgM Level

Immunity Biomarker

Sample Needed

Collection Type: Blood

Body System

Related System: Immunity

Overview

Immunoglobulin M (IgM) is a large antibody produced by B cells as the first-line humoral response to a new or recent infection. A serum IgM level measures the concentration of this antibody in blood and helps distinguish acute/recent infection from past exposure (which is often marked by IgG). Elevated IgM can suggest acute viral or bacterial infection, certain autoimmune diseases, liver disease, or an IgM-secreting monoclonal gammopathy. Low IgM may indicate primary immunodeficiency, protein loss, or immunosuppression. Indications for testing include new infectious symptoms, recurrent infections, unexplained systemic illness, or evaluation of immune status. Levels vary with age (infants and young children have different reference ranges), and are only mildly affected by sex; elderly may show modest changes.

People also test for

Test Preparation

No special preparation is required

Why Do I Need This Test

Profile: Immunity (immunoglobulin panel) - Symptoms: recent fever, sore throat, unusual infections, fatigue, swollen lymph nodes, visual changes or neurological signs suggesting hyperviscosity - Diagnoses/monitoring: acute/recent infection, immune deficiency, autoimmune disease, monoclonal gammopathy (IgM paraproteinemia) - Reasons for abnormal levels: acute infection, chronic inflammation, liver disease, monoclonal proliferation (high); primary immunodeficiency, protein-losing states, immunosuppressant drugs (low) - Lifestyle/family: heavy alcohol use, malnutrition, or family history of immunodeficiency/hematologic disorders may prompt testing

Run our symptom checker to see if this test is right for you

Symptom Checker

Understanding Test Results

Low IgM (<40 mg/dL): mild deficiency (20–39 mg/dL) may increase susceptibility to some infections; severe deficiency (<20 mg/dL) suggests common variable or selective IgM deficiency, primary immunodeficiency, or significant protein loss (nephrotic syndrome) and warrants further immunologic workup.
Normal (40–230 mg/dL): consistent with expected acute-phase capacity; interpret with clinical context and other immunoglobulins (IgG, IgA).
Mild-to-moderate elevation (231–500 mg/dL): often seen in acute or recent infections and autoimmune/inflammatory conditions; usually polyclonal.
Marked elevation (>500–1000 mg/dL): raises concern for chronic immune stimulation, liver disease, or monoclonal gammopathy.
Very high (>1000 mg/dL): suspicious for IgM monoclonal gammopathy such as Waldenström’s macroglobulinemia or other plasma cell dyscrasias; may cause hyperviscosity symptoms and requires urgent hematology evaluation.
Interpretation must consider age, symptoms, and electrophoresis/immunofixation results.

Normal Range

40-230 mg/dL OR 0.4-2.3 g/L

FAQs

Q: What is an IgM level?

A: IgM level measures the concentration of immunoglobulin M, the body's first antibody produced in response to infection. Measured in blood, high IgM suggests recent or acute infection or immune activation; low IgM can indicate an antibody deficiency. Results are reported in mg/dL or g/L and must be interpreted with symptoms and other tests (IgG, IgA, specific serology) by a clinician.

Q: What happens when IgM is high?

A: High IgM usually indicates a recent or acute immune response, often from infection, but can also reflect autoimmune conditions, chronic liver disease, or monoclonal B‑cell disorders like Waldenström macroglobulinemia or MGUS. Very high monoclonal IgM may cause hyperviscosity symptoms (headache, vision changes, bleeding) and needs urgent evaluation. Follow‑up tests and specialist review determine the cause and treatment.

Q: What is meant by IgM positive?

A: IgM positive means that immunoglobulin M antibodies to a specific pathogen are detectable in your blood. IgM is the body’s first antibody response, so a positive result usually indicates recent or current (acute) infection or recent exposure. Results can sometimes be false positive or nonspecific, so confirmatory testing (including IgG or repeat testing) and clinical correlation are recommended; consult a healthcare professional.

Q: What is IgM important for?

A: IgM is the body’s first antibody produced in a new (primary) infection. Its pentameric structure makes it excellent at agglutinating pathogens and activating the classical complement pathway, promoting early clearance of microbes. Detection of IgM in blood usually indicates recent or acute infection. IgM is produced by B cells and does not cross the placenta, so maternal IgM doesn't confer fetal immunity.

Q: How do you treat high IgM levels?

A: Treatment for high IgM depends on the cause. Acute infections are treated with appropriate antimicrobials; monoclonal IgM disorders (e.g., Waldenström’s) may need chemotherapy, rituximab and plasmapheresis for hyperviscosity. Autoimmune causes use immunosuppression. Primary hyper‑IgM immunodeficiency is managed with immunoglobulin replacement, prophylactic antibiotics and sometimes stem‑cell transplant. See a hematologist/immunologist for diagnosis and tailored therapy.

Q: How to cure IgM positive?

A: IgM positivity indicates a recent or acute infection; there is no single “cure.” Management depends on the specific cause: your clinician can prescribe targeted therapy (antivirals or antibiotics when appropriate), plus rest, fluids, symptom control and infection precautions. Repeat serology and follow-up are often needed to confirm resolution or conversion to IgG. Seek urgent care if symptoms worsen or complications develop.