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Lymphocyte count by automated blood cell differential (complete blood count component)

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

This test measures the number of lymphocytes, a type of white blood cell, in your blood. Lymphocytes help fight infections and maintain immune function.

Quick summary

["Your doctor may use this test to check for immune system issues or infections."]

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

Key facts at a glance

LOINC
107155-4
Short code
Lymphocytes # HPC BPU
Synonyms
Lymphocytes # HPC BPU
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors order lymphocyte counts to diagnose or monitor conditions affecting the immune system, such as infections, autoimmune diseases, or blood disorders. It may also be part of routine blood work or follow-up testing after treatment for cancer or other illnesses.

What to Expect Before the Test

No special preparation is needed. You’ll typically have a small needle inserted into your arm to draw blood, similar to other blood tests. If you’re on blood-thinning medication, let your doctor know before the test.

How the Test Works

Blood is drawn and analyzed using an automated machine that separates and counts different types of white blood cells, including lymphocytes. This process is quick and painless.

Possible Results and Interpretation

Results are usually reported as a count of lymphocytes per microliter (cells/mcL) of blood. While reference ranges vary by lab, lower than expected counts may suggest immune suppression, while higher counts could indicate infection, inflammation, or other conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low lymphocyte counts may signal weakened immunity, often seen in conditions like HIV/AIDS, chemotherapy side effects, or severe infections. High counts can be linked to chronic infections, certain cancers (e.g., lymphoma), or inflammatory diseases. Abnormal results prompt further evaluation to identify underlying causes.

Short name

Lymphocyte count

Frequently asked questions

What causes a low lymphocyte count?
Low lymphocyte counts can result from infections (like COVID-19 or tuberculosis), certain medications (e.g., steroids, chemotherapy), autoimmune diseases, or conditions affecting bone marrow function. Chronic stress or sleep deprivation may also temporarily reduce lymphocyte levels.
What causes a high lymphocyte count?
High lymphocyte counts often appear during acute infections (e.g., viral infections like mononucleosis), chronic inflammatory diseases (e.g., rheumatoid arthritis), or certain cancers (e.g., leukemia). Stress, allergies, or exposure to toxins may also elevate lymphocyte numbers.
Can lifestyle changes affect lymphocyte counts?
Yes. A balanced diet rich in vitamins (e.g., folate, vitamin B12), regular exercise, and adequate sleep can support immune function. Avoiding smoking and limiting alcohol may also help maintain stable lymphocyte levels. Stress management techniques, like meditation or therapy, can indirectly support immune 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