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B-cell Immunoglobulin M (IgM) Quantification in Whole Blood

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

This test measures the amount of Immunoglobulin M (IgM), a type of antibody produced by B-cells, in your blood. IgM is often elevated in response to infections or certain immune system conditions.

Quick summary

["IgM antibodies help your immune system fight infections, and this test helps track their presence and levels."]

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

Key facts at a glance

LOINC
89345-3
Short code
CD19IGM
Synonyms
CD19+IgM+ cells # Bld
Category
chemistry
Sample
whole-blood
Container
EDTA (lavender/purple-top) tube; alternatively sodium heparin (green-top) tube for flow cytometry applications
Units
N/A
Ref low
5
Ref high
225
Fasting
false
Population
adult
Sex
all
Age range
0–999 years
Method
Flow cytometry using fluorescently labeled monoclonal antibodies against CD19 and surface IgM, with absolute count determination using counting beads or volumetric measurement
CPT
86355
SNOMED
269751007
Specimen volume
2-5 mL whole blood for adults; 1-3 mL for pediatric patients
Stability
Specimen must be processed within 24-48 hours of collection when stored at room temperature (20-25°C). Refrigeration (2-8°C) may extend stability to 48 hours but may affect cell viability and surface marker expression.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–48 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like frequent infections, fatigue, or swelling in lymph nodes. It could also be used to monitor conditions such as chronic infections, autoimmune diseases, or certain cancers like lymphoma.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast before the test, but this depends on the lab’s instructions. Bring any medications you’re currently taking to your appointment.

How the Test Is Performed

A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a brief pinch, but it usually doesn’t cause discomfort afterward. The blood sample is then sent to a lab for analysis.

What the Results Mean

Results are typically reported as a concentration of IgM in your blood. Higher than normal levels may indicate an active infection, immune system response, or certain medical conditions. Lower levels might suggest immune system issues or certain genetic disorders.

Reference range

Reference ranges vary by age; adult values typically 5-225 cells/μL (absolute count). CD19+IgM+ cells represent naïve and transitional B lymphocytes. Pediatric reference ranges are generally higher than adult values, with progressive decline throughout childhood.N/A

Specimen: whole-blood

No special preparation required. Specimen should be collected and processed within 24 hours for optimal viability. Recent vaccination, infection, or immunosuppressive therapy may affect results and should be noted on the requisition.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Elevated IgM levels can signal recent or ongoing infections (e.g., hepatitis, mononucleosis), immune disorders (e.g., lupus, rheumatoid arthritis), or conditions like chronic lymphocytic leukemia. Low IgM levels may be associated with immune deficiencies or certain genetic disorders. Always discuss your results with your healthcare provider for an accurate interpretation.

Short name

IgM B-Cell Level

Frequently asked questions

How long does it take to get the results?
Results are usually available within 1 to 3 business days, depending on the lab’s processing time. Some labs may provide preliminary results sooner, but confirm with your healthcare provider or lab for exact timelines.
Can I eat or drink before this test?
Most labs do not require fasting for this test, but it’s best to follow specific instructions from your healthcare provider or the lab. Generally, you can eat and drink normally unless advised otherwise.
Is there any risk or discomfort associated with this test?
The most common discomfort is a slight pinch when the needle is inserted. There may be mild bruising or soreness at the injection site, but these are usually temporary. Rarely, some people experience fainting or dizziness when blood is drawn. Inform your healthcare provider if you experience any unusual symptoms.
  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