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CD8+ T Lymphocyte Count (Peripheral Blood)

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

This test measures the number of CD8+ T cells in your blood, which are a type of immune cell that helps fight infections and cancer.

Quick summary

["CD8+ T cells play a key role in your immune defense and may be checked if you have symptoms of immune disorders or cancer."]

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

Key facts at a glance

LOINC
80222-3
Short code
CD8LYM
Synonyms
CD8 Cells/lymph NFr Spec
Category
chemistry
Sample
serum
Container
EDTA (lavender/purple-top) tube for whole blood flow cytometry; alternatively sodium heparin (green-top) tube
Units
N/A
Ref low
150
Ref high
1000
Critical range
100 N/A – 3000 N/A
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Flow cytometry with fluorescent monoclonal antibody staining (immunophenotyping) using CD3 and CD8 markers, typically performed on whole blood with lymphocyte gating strategy
CPT
86359 (T cells, total count); 86360 (T cells, absolute CD4 and/or CD8 count); additional codes may apply for percentage enumeration
SNOMED
14240001 | 250528004 | 37745000
Specimen volume
3-5 mL whole blood (minimum 1 mL for pediatric samples)
Stability
Room temperature: 24-48 hours; Refrigerated (2-8°C): up to 48 hours; Do not freeze. Specimen viability decreases significantly after 48 hours.
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may order this test if you have symptoms like fatigue, frequent infections, or unexplained weight loss. It could also be part of a routine check-up or monitoring for conditions like HIV, certain cancers, or autoimmune diseases.

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 small amount of blood. This is usually done in a clinic or lab.

What the Results Mean

Results show the count of CD8+ T cells in your blood. Lower than expected counts may indicate immune suppression, while higher counts might suggest certain immune responses or conditions.

Common Conditions Monitored

This test is often used to monitor immune function in people with HIV/AIDS, cancer patients undergoing treatment, or those with autoimmune diseases.

Reference range

CD8+ T-lymphocytes: 150-1000 cells/μL (absolute count); 15-40% of total lymphocytes; CD8/CD3 ratio typically 0.20-0.50N/A

Specimen: serum

No fasting required. Avoid strenuous exercise 24 hours prior to collection. Recent vaccinations, infections, or immunosuppressive therapies may affect results and should be documented. Specimen should be processed within 24-48 hours of collection for optimal viability.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

CD8+ T cells are crucial for immune surveillance and response. Low levels can signal weakened immunity, while elevated levels may be seen in chronic infections or certain cancers. Always discuss results with your healthcare provider for personalized interpretation.

Short name

CD8+ T Cells

Frequently asked questions

What causes CD8+ T cell counts to change?
CD8+ T cell counts can be affected by infections, immune system disorders, certain medications, or underlying health conditions like cancer or HIV. Stress, illness, or recent vaccinations may also temporarily influence these levels.
How often should I get this test?
Your healthcare provider will determine the frequency based on your health needs, treatment plan, or symptoms. Regular monitoring may be recommended if you have a chronic condition or are undergoing treatment for one.
Can I eat or drink before this test?
You can eat and drink normally before this test, as no special diet or fasting is required.
  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