Immunoglobulin M (IgM) in Serum or Plasma
This test measures the amount of Immunoglobulin M (IgM) antibodies in your blood. IgM is one of the types of antibodies your immune system produces to fight infections.
["IgM helps identify recent infections and immune responses."]
Key facts at a glance
- LOINC
- 108728-7
- Short code
- IgE Msmt SerPl
- Synonyms
- IgE Msmt SerPl
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What Does IgM Measure?
IgM antibodies are typically produced early in an infection to help your body fight pathogens like viruses, bacteria, or parasites. They are part of your immune system’s first line of defense and can linger in your bloodstream for months or even years after the infection has cleared.
Why Might Your Doctor Order This Test?
Your doctor may request an IgM test to diagnose or monitor conditions such as acute infections (e.g., viral hepatitis, measles, or mononucleosis), autoimmune diseases, or to check for past exposure to certain pathogens. It can also help assess immune system function or response to treatment.
Common Uses in Healthcare
IgM testing is often used alongside other blood tests (like IgG or IgA) to provide a fuller picture of your immune response. For example, it can help distinguish between recent and past infections or identify immune system disorders.
What to Expect Before the Test
No special preparation is usually needed. You may have a small needle inserted into a vein (venipuncture) to draw blood, or a blood sample may be collected from your finger. If you’re on blood-thinning medication, let your doctor know before the test.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated IgM levels often indicate an active infection or an ongoing immune response. Low IgM levels may suggest immune deficiencies or certain genetic disorders. Your doctor will interpret results in the context of your medical history, symptoms, and other tests.
Short name
IgM Level
Frequently asked questions
How long does it take to get results?
Can IgM levels change over time?
Does diet or exercise affect IgM levels?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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