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Immunoglobulin M (IgM) by Turbidimetry (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 your immune system produces in response to infections.

Quick summary

["IgM helps your body fight infections and can indicate past or recent exposure to certain pathogens."]

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

Key facts at a glance

LOINC
111412-3
Short code
IgM Msmt Ur
Synonyms
IgM Msmt Ur
Category
chemistry
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
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 key proteins in your immune system that helps fight infections. It appears early in the body’s response to new infections and can linger longer than other antibodies. This test checks your blood for IgM levels, which can help doctors understand how your immune system is responding to illness or infection.

Why Might You Need This Test?

Your doctor may order this test to diagnose or monitor conditions like infections (e.g., hepatitis, mononucleosis), autoimmune diseases, or certain cancers. IgM levels can also help track how well a treatment is working or if an infection is spreading.

How Is the Test Performed?

A small blood sample is taken from a vein in your arm. The blood is then processed to measure IgM levels using a turbidimetric method, which detects changes in light scattering caused by the antibodies in your serum or plasma.

What Are Possible Results?

Results may be compared to standard reference ranges to identify elevated or low IgM levels, which can signal different health conditions. However, reference ranges can vary by lab, so your doctor will interpret results in the context of your overall health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Elevated IgM levels may suggest recent infections, chronic immune responses, or certain autoimmune disorders. Low IgM levels could indicate immune system dysfunction or deficiencies. Your doctor will use these results alongside other tests and symptoms to guide diagnosis and treatment.

Short name

IgM Level (Turbidimetric)

Frequently asked questions

What Does an Elevated IgM Level Mean?
An elevated IgM level often points to an active infection (like hepatitis or a viral illness) or a condition where your immune system is overreacting. It may also appear in some autoimmune diseases or cancers, so further testing is usually needed to determine the cause.
What Does a Low IgM Level Mean?
Low IgM levels may suggest a weakened immune system, genetic disorders affecting antibody production, or certain medications that suppress immune function. This isn’t always a cause for concern, but your doctor will assess it in relation to your health history.
Can IgM Levels Change Over Time?
Yes, IgM levels can fluctuate depending on your health status. For example, they may rise during an infection and then decline as your body clears the infection. Repeated testing can help track progress, especially in chronic conditions or treatment monitoring.
  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