B-cell Count in Whole Blood
This test measures the number of B-cells (a type of white blood cell) in your blood. B-cells play a key role in the immune system by producing antibodies to fight infections.
["B-cell counts help assess immune function and identify potential immune disorders."]
Key facts at a glance
- LOINC
- 25164-5
- Short code
- CD21
- Synonyms
- CD21 Cells # Bld
- Category
- chemistry
- Sample
- whole-blood
- Container
- EDTA (lavender/purple-top) tube or ACD (yellow-top) tube for flow cytometry; sodium heparin tube may also be acceptable per laboratory protocol
- Units
- N/A
- Ref low
- 90
- Ref high
- 400
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Flow cytometry using fluorescently labeled monoclonal antibodies (CD21) with absolute count determination via dual-platform or single-platform methods
- CPT
- 86356
- SNOMED
- 39871000146108
- Specimen volume
- 3-5 mL whole blood (adult); minimum 1 mL (pediatric); sample volume requirements vary by laboratory
- Stability
- Specimen should be processed within 24-30 hours of collection when stored at room temperature (18-25°C); do not refrigerate as cold may affect cell viability and surface antigen expression
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 24–72 hours
- Order
- routine
Why This Test Might Be Ordered
Your healthcare provider may recommend this test if you have symptoms like frequent infections, unexplained fatigue, or if you’re being evaluated for conditions such as immune deficiencies, autoimmune diseases, or certain cancers like lymphoma.
What to Expect Before the Test
No special preparation is usually needed. You’ll have a small needle inserted into your arm or vein to draw a blood sample. The process is quick and typically painless.
What the Results Mean
Results are compared to standard ranges for healthy adults. Low B-cell counts may indicate immune system issues, while very high counts could signal overactive immune responses or certain diseases.
Common Conditions Linked to B-Cell Counts
Abnormal B-cell counts can be linked to conditions like chronic infections, autoimmune diseases (e.g., lupus), or blood disorders. Persistent changes may warrant further medical evaluation.
Reference range
Reference ranges vary by laboratory and age; CD21+ B-cell absolute counts typically reported as cells/μL. Adult normal range approximately 90-400 cells/μL (varies by reference laboratory methodology)N/A
No fasting required. Specimen should be collected prior to corticosteroid administration if possible, as corticosteroids may transiently affect lymphocyte subset counts. Avoid strenuous exercise immediately prior to collection.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
B-Cell Count
Frequently asked questions
How often should I expect this test if I have recurring infections?
Can diet or supplements affect B-cell counts?
Is there any risk or discomfort with this blood test?
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