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CD3+ T Cell Count (from Whole Blood)

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

This test measures the number of CD3+ cells, a type of white blood cell that plays a key role in immune responses. CD3+ cells are part of the T lymphocyte family, which helps the body fight infections and regulate immune responses.

Quick summary

["Understanding your T cell count helps assess your immune health and response to treatments."]

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

Key facts at a glance

LOINC
13848-7
Short code
CD3CD26
Synonyms
CD3+CD26+ Cells # Bld
Category
chemistry
Sample
whole-blood
Container
EDTA (lavender/purple-top) blood collection tube for flow cytometry immunophenotyping
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
0–99 years
Method
Flow cytometry using fluorescently labeled monoclonal antibodies targeting CD3 and CD26 surface markers
CPT
86359
SNOMED
399022008
Specimen volume
3-5 mL of whole blood; minimum 1 mL for pediatric samples
Stability
Specimen should be processed within 24-30 hours of collection when stored at room temperature (18-25°C). Do not refrigerate. Viability and marker expression may decline with prolonged storage.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
24–72 hours
Order
routine

Why This Test Is Done

Doctors may order a CD3+ T cell count to evaluate immune function, monitor conditions like HIV/AIDS, check for immune deficiencies, or assess responses to cancer treatments (e.g., chemotherapy or immunotherapy). It can also be used in diagnosing autoimmune diseases or infections.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for a few hours before the blood draw, but this depends on your healthcare provider’s instructions. Bring a list of medications you’re currently taking.

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 slight prick, but the procedure is quick and typically painless. The blood sample is then sent to a lab for analysis.

What the Results Mean

Results are reported as a count of CD3+ cells per microliter (cells/µL) of blood. Lower than expected counts may indicate immune suppression, while higher counts could suggest certain immune conditions or inflammation. Your results will be interpreted by your doctor in the context of your overall health.

Reference range

Reference ranges vary by laboratory; CD3+CD26+ cells typically represent a subset of activated T lymphocytes. Values are reported as absolute counts (cells/μL) and may vary by age. Consult laboratory-specific reference ranges.N/A

Specimen: whole-blood

No special patient preparation required. Fasting is not necessary. Patients should inform their healthcare provider about recent infections, vaccinations, or immunosuppressive medications, as these may affect lymphocyte subset populations.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Abnormally low CD3+ T cell counts can signal immune deficiencies, such as severe combined immunodeficiency (SCID) or HIV/AIDS progression. High counts may be seen in chronic infections, certain autoimmune diseases, or after immune-stimulating treatments. Regular monitoring is critical for patients undergoing treatments that affect the immune system.

Short name

T Cell Count

Frequently asked questions

How long does it take to get my test results?
Test results are typically available within 1 to 3 business days, depending on your lab’s processing time. Your doctor will contact you once the results are ready, either through a phone call or secure message system.
What does a low CD3+ T cell count mean?
A low CD3+ T cell count may suggest an immune system that isn’t functioning as well as it should, which can increase your risk of infections. This could be due to conditions like HIV/AIDS, certain cancers, or treatments that suppress the immune system (e.g., chemotherapy). Your doctor will discuss possible causes and next steps with you.
Can I eat or drink before this test?
Most tests like this do not require fasting, but always follow your doctor’s or lab technician’s specific instructions. If you’re unsure, ask before your appointment to avoid any delays or errors in results.
  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