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Lymphocyte count (peripheral blood)

Published: August 9, 2026Updated: August 15, 2026

This test measures the number of lymphocytes, a type of white blood cell important for fighting infections and maintaining immune function.

Quick summary

["Lymphocytes help protect your body from illness and infection."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 15, 2026Editorial policy

Key facts at a glance

LOINC
73901-1
Short code
CD57FC
Synonyms
CD3-CD8-CD57+/lymph NFr Bld FC
Category
chemistry
Sample
whole-blood
Container
EDTA (lavender/purple-top) anticoagulant tube. ACD (yellow-top) tube is also acceptable. Sodium heparin (green-top) may be used for some flow cytometry panels.
Units
N/A
Ref low
2
Ref high
10
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
flow-cytometry
CPT
86356
SNOMED
399068008
Specimen volume
3-5 mL whole blood (minimum 1 mL for pediatric samples). Adequate sample is required to obtain sufficient lymphocyte events for accurate analysis.
Stability
Specimen should be processed within 24-48 hours of collection when stored at room temperature (18-25°C). Refrigerated storage (2-8°C) may extend viability up to 72 hours, but optimal results are obtained with fresh specimens analyzed within 24 hours.
Hemolysis max
100
Lipemia max
100
Icterus max
50
TAT
24–72 hours
Order
routine

What Are Lymphocytes?

Lymphocytes are a key component of your immune system. They include B cells, T cells, and natural killer cells, each playing a role in recognizing and responding to pathogens like viruses, bacteria, and even cancer cells. Your body produces lymphocytes in the bone marrow and lymph nodes, and they circulate through your blood and lymphatic system to defend against threats. Abnormal lymphocyte counts can signal immune system issues, infections, or other health conditions.

Why Might You Need This Test?

Doctors may order a lymphocyte count to diagnose or monitor conditions such as infections (like HIV or tuberculosis), autoimmune diseases (like lupus or rheumatoid arthritis), cancers (like lymphoma or leukemia), or to assess immune function before treatments like chemotherapy.

How Is the Test Performed?

A small sample of your blood is drawn from a vein, usually in your arm. The blood is then analyzed in a lab to count the number of lymphocytes. This test is quick and typically done as part of a routine blood test or specific diagnostic workup.

What Do Results Mean?

Results are usually reported as a count of lymphocytes per microliter (µL) of blood. While reference ranges can vary slightly by lab, a lower than expected count may indicate immune suppression, infection, or certain cancers. A higher than expected count might suggest overactive immune responses, such as in certain infections or inflammatory conditions.

Reference range

CD3- CD8- CD57+ lymphocytes: 2-10% of total lymphocytes (approximately 40-200 cells/μL). Reference ranges vary by laboratory and should be interpreted with clinical context.N/A

Specimen: whole-blood

No special preparation required. Recent immunizations, immunosuppressive therapy, or active infections may affect results. Inform the laboratory of any immunomodulatory medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Abnormal lymphocyte counts can provide critical clues about underlying health issues. For example, a low lymphocyte count might suggest immune deficiency, while a high count could indicate chronic infections, inflammatory diseases, or even certain types of cancer. Regular monitoring of lymphocyte counts is important for patients undergoing treatments that suppress the immune system, such as chemotherapy or organ transplants.

Short name

Lymphocyte count

Frequently asked questions

What causes a low lymphocyte count?
Low lymphocyte counts can be caused by infections (like HIV or severe viral illnesses), certain medications (such as steroids), autoimmune diseases, or conditions that affect the bone marrow’s ability to produce white blood cells. It may also occur in people with chronic illnesses or those undergoing treatments that weaken the immune system.
What causes a high lymphocyte count?
High lymphocyte counts are often seen in infections (like mononucleosis or tuberculosis), certain cancers (like lymphoma), or autoimmune diseases where the immune system overreacts. Chronic inflammation or exposure to toxins may also lead to elevated lymphocyte levels.
How often should I get this test?
The frequency of testing depends on your medical condition and treatment plan. If you have a chronic illness, your doctor may recommend periodic checks. For example, people with HIV, cancer, or autoimmune diseases might need regular monitoring to adjust treatments as needed.
  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 15, 2026. · Read our editorial policy