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Lymphocyte count (manual differential blood count)

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

This test measures the types and proportions of white blood cells called lymphocytes in your blood, which are part of your immune system. It helps assess immune function and identify potential infections or disorders.

Quick summary

["Understanding your lymphocyte types can help diagnose immune-related conditions."]

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

Key facts at a glance

LOINC
21373-6
Short code
Lymph Abn NFr Snv Manual
Synonyms
Lymph Abn NFr Snv Manual
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
manual-count
Specimen volume
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors may order a lymphocyte differential when they suspect an infection, autoimmune disease, or other conditions affecting your immune system. It can also be part of routine blood work for monitoring chronic illnesses like cancer or HIV.

How the Test Works

A small blood sample is taken from your arm. A technician will then manually examine the blood under a microscope to count and categorize different types of lymphocytes (B cells, T cells, and natural killer cells). This process provides detailed information about immune cell distribution.

What to Expect Before the Test

No special preparation is usually needed, but you may want to avoid strenuous activity 24 hours before the test. If you’re on blood-thinning medications, let your doctor know.

What the Results Mean

Results show the percentage or absolute count of each lymphocyte type. Abnormal levels may indicate conditions like lymphoma, leukemia, or immune deficiencies. Your doctor will interpret these results in the context of your overall health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Lymphocyte Differential

Frequently asked questions

What causes abnormal lymphocyte counts?
Abnormal lymphocyte counts can result from infections (e.g., viral like HIV or Epstein-Barr), autoimmune diseases (e.g., lupus), or blood disorders (e.g., leukemia). Chronic illnesses like cancer or long-term stress may also affect lymphocyte levels.
How often should I get this test?
Frequency depends on your health condition. Doctors may recommend periodic testing if you have a chronic illness, are undergoing treatment for cancer or HIV, or have symptoms like frequent infections.
Can lifestyle changes affect lymphocyte counts?
Yes, diet, sleep, and stress levels can influence immune function. Maintaining a balanced diet, staying hydrated, and managing stress may support normal lymphocyte levels, but this test is not a direct measure of lifestyle impact.
  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