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Immunoglobulin M (IgM) in Whole Blood by Manual Immunoassay

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

This test measures the level of Immunoglobulin M (IgM) in your blood. IgM is a type of antibody that helps your immune system fight infections, including viruses and bacteria.

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
33841-8
Short code
Imm Moncytes # Bld Manual
Synonyms
Imm Moncytes # Bld Manual
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
manual-count
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 Does IgM Measure?

IgM is one of the key proteins produced by your immune system when you are fighting an infection. It appears early in the immune response and can linger longer than other antibodies, making it useful for detecting recent infections or chronic conditions.

Why Might You Need This Test?

Doctors may order an IgM blood test to diagnose or monitor conditions such as infections (like hepatitis, HIV, or certain viral infections), autoimmune diseases, or to check for immune system responses after vaccination.

Sample Collection and Testing Process

A blood sample is taken from a vein in your arm. The sample is then processed and tested using a manual immunoassay method to detect IgM antibodies. This test does not require fasting.

What Are Possible Results?

Results can vary based on your health condition, age, and other factors. Elevated IgM levels may suggest recent infection or certain immune-related conditions, while normal levels do not necessarily mean you are healthy.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgM Blood Test

Frequently asked questions

Why might my IgM levels be higher than expected?
Higher IgM levels can be seen in recent infections (like viral or bacterial infections), chronic infections, or autoimmune diseases. It may also appear after vaccination or exposure to certain toxins. Your doctor will discuss these findings with you based on your medical history and symptoms.
Could low IgM levels affect my health?
Low IgM levels may indicate a weakened immune system, which can make you more susceptible to infections. This could be due to genetic conditions, certain medications, or underlying health issues. Your doctor will evaluate this in the context of your overall health.
How often should I get this test?
The frequency of IgM testing depends on your medical condition and treatment plan. If you have an ongoing health issue, your doctor may recommend periodic testing. If you're healthy, this test is usually not routinely recommended unless symptoms suggest an infection or immune issue.
  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