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Immunoglobulin M (IgM) antibody concentration in blood

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, including some viruses and bacteria.

Quick summary

["IgM antibodies can help identify recent infections or immune responses."]

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

Key facts at a glance

LOINC
14002-0
Short code
IgM BldCo-aCnc
Synonyms
IgM BldCo-aCnc
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What Is Immunoglobulin M (IgM)?

IgM is one of the main types of antibodies produced by your immune system. It plays a key role in defending against infections, especially those caused by bacteria and some viruses. IgM levels can rise when your body is fighting an infection or responding to an immune challenge.

Why Might You Need This Test?

Doctors may order an IgM antibody test to diagnose or monitor conditions such as infections (like hepatitis, Lyme disease, or mononucleosis), autoimmune diseases, or certain blood disorders. It can also help track immune responses after vaccination or treatment.

When Could You Expect Results?

Results for IgM antibody tests are typically ready within a few days to a couple of weeks, depending on lab processing times. Your healthcare provider will discuss the results with you during your follow-up visit.

What Does a High or Low IgM Level Mean?

Elevated IgM levels may suggest recent infection, chronic immune activation, or certain autoimmune conditions. Lower-than-normal IgM levels might indicate immune system dysfunction or certain genetic disorders.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: IgM Antibodies and Health

Short name

IgM Antibody Level

Frequently asked questions

What causes IgM levels to change?
IgM levels can increase due to active infections (like bacterial or viral illnesses), immune system responses (such as after vaccination), or certain chronic conditions like autoimmune diseases. They may also be lower in people with weakened immune systems or specific genetic disorders.
How long do IgM levels stay elevated?
IgM levels typically rise during an infection and may stay elevated for weeks to months, depending on the illness and how your body responds. They often return to normal as the infection resolves.
Can IgM levels be affected by medications?
Yes, some medications—such as certain immunosuppressants or chemotherapy drugs—may influence IgM production. Always discuss any medications you’re taking with your healthcare provider, as they could impact test 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