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CD4 T-Cell Count (Per Microliter) from Whole Blood

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

This test measures the number of CD4 T-cells in your blood. CD4 cells are a type of white blood cell that plays a key role in helping your immune system fight infections and diseases.

Quick summary

["CD4 cells help protect your body’s immune system and are often checked in people with weakened immune systems."]

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

Key facts at a glance

LOINC
104694-5
Short code
CD40FC
Synonyms
CD40 Cells Bld Ql FC
Category
chemistry
Sample
whole-blood
Container
EDTA (purple-top) or heparin (green-top) anticoagulated blood collection tube. ACD (yellow-top) tube is also acceptable. Sodium heparin is generally preferred for flow cytometry immunophenotyping to preserve cell viability and antigen expression.
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
flow-cytometry
CPT
86356
SNOMED
395124003
Specimen volume
3-5 mL of whole blood for adults; 1-2 mL for pediatric patients. Minimum 1 mL recommended to ensure adequate cell yield for analysis.
Stability
Specimen should be processed within 24-48 hours of collection when stored at room temperature (18-25°C). Refrigeration (2-8°C) may extend stability to 48-72 hours for some markers but can affect certain antigen expression. Do not freeze. Optimal viability and antigen preservation is achieved when analyzed within 24 hours of collection.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
24–72 hours
Order
routine

Why This Test Is Done

Your healthcare provider may order this test if you have a weakened immune system, are at risk for infections, or have conditions like HIV/AIDS, certain cancers, or long-term use of immune-suppressing medications. It can also be used to monitor treatment progress or response to therapy.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or hand to draw a blood sample. The process is quick and usually painless. If you’re nervous, let your provider know—they can offer options to make it more comfortable.

What the Test Results Mean

Results are typically reported as a count of CD4 cells per microliter (µL) of blood. Lower counts may indicate a weaker immune response, while higher counts suggest a stronger immune system. However, your provider will interpret results based on your specific health needs.

Common Causes of Abnormal Results

Low CD4 counts can be caused by conditions like HIV infection, certain cancers, autoimmune diseases, or long-term use of steroids or chemotherapy. High counts may be normal or could indicate conditions like chronic infections or certain immune disorders.

Reference range

Results reported as presence or absence of CD40-positive cells in peripheral blood. Reference ranges vary by laboratory; typically reported as percentage of lymphocytes or absolute count (cells/μL). Normal expression is expected on B-lymphocytes, monocytes, and dendritic cells. Consult laboratory-specific reference interval for quantitative values.N/A

Specimen: whole-blood

No special patient preparation required. Fasting is not necessary. Patients should be informed that the test requires a blood draw. Recent immunosuppressive therapy, chemotherapy, or monoclonal antibody treatment (e.g., anti-CD40 therapy) may affect results and should be disclosed to the ordering physician.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CD4 Cell Count

Frequently asked questions

What does a low CD4 count mean for my health?
A low CD4 count (often below 500 cells/µL) may signal an immune system that’s less able to fight infections. In people with HIV, very low counts (below 200 cells/µL) can lead to serious infections or diseases, like tuberculosis or certain cancers. Your provider will guide you on what these results mean for your care plan.
How often should I get this test?
The frequency depends on your health status. If you have HIV, your provider may recommend regular testing to monitor your immune health and adjust treatment as needed. Others with weakened immune systems might need testing less often, but your provider will determine the best schedule for you.
Can diet or lifestyle affect CD4 cell counts?
While diet and lifestyle factors like smoking, alcohol, or poor sleep can impact overall health, they don’t directly affect CD4 cell counts. However, maintaining a healthy lifestyle can support your immune system indirectly. Always follow your provider’s advice for managing your health.
  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