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Immunoglobulin M (IgM) Total Antibody Level in Serum/Plasma

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of Immunoglobulin M (IgM) antibodies in your blood. IgM is a type of antibody that helps your immune system fight infections.

Quick summary

["IgM helps identify recent infections and immune responses."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
68975-2
Short code
IgM.IT/IgM.total MFr CSF
Synonyms
IgM.IT/IgM.total MFr CSF
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

What Is IgM Used For?

IgM antibodies are typically produced early in an infection. Your doctor may order this test to help diagnose recent infections, such as viral or bacterial illnesses, or to assess immune responses to certain conditions like autoimmune diseases or chronic infections.

When Might You Need This Test?

You might need this test if you have symptoms of an infection (like fever, fatigue, or swollen lymph nodes), if you’ve been exposed to a known pathogen, or if your doctor suspects a condition affecting your immune system. It can also be part of monitoring for certain chronic illnesses.

How Is the Test Done?

A blood sample is taken from a vein in your arm. The blood is then processed to separate serum or plasma, where the IgM antibodies are measured using an immunoassay method. This test is usually done in a lab and results are available within a few days.

What Do the Results Mean?

Elevated IgM levels may suggest an ongoing infection, an immune response to a vaccine, or certain autoimmune conditions. Lower-than-expected levels might indicate immune system issues or certain genetic disorders. Your doctor will interpret the results in the context of your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: IgM plays a key role in early immune defense. High IgM levels can indicate recent infections (e.g., hepatitis, measles, or other viral/bacterial illnesses), while chronic infections (e.g., HIV, Lyme disease) may also show elevated IgM. It can also help diagnose autoimmune conditions or monitor immune function in certain diseases.

Short name

IgM Antibody Test

Frequently asked questions

Why might my IgM test be ordered if I don’t have symptoms of an infection?
Your doctor may order this test for screening, monitoring a known condition, or investigating unexplained symptoms. For example, it could be part of a routine checkup, a follow-up for a suspected infection, or to assess immune function in conditions like lupus or HIV.
Can IgM levels change over time, and how long do they stay elevated?
Yes, IgM levels can fluctuate depending on the infection or immune response. They often peak within weeks of an infection and gradually decline as the body resolves the illness. The duration of elevated levels varies—some infections may take months or longer to clear, while others resolve faster.
Is there anything I should avoid before my IgM test?
No specific preparations are needed for this test, but avoid taking certain medications (like steroids) that could affect immune function unless instructed by your doctor. If you have a recent infection or vaccination, mention it to your healthcare provider, as it may impact results.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy