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Immune defense

White Blood Cell Count

Also known as: Leukocyte count, WBC test, White cell count

A white blood cell (WBC) count measures the number of white blood cells in your blood. These cells are key components of your immune system that defend against infections and other foreign invaders. 

White blood cells are made in bone marrow and found in blood and lymph tissue.

This test is part of a complete blood count (CBC), one of the most common lab panels ordered during checkups or when evaluating symptoms like fatigue, fever, or inflammation. Providers use it to detect infection, monitor chronic illness, and track the effects of treatments that affect the immune system.

Telehealth providers can order and review your CBC results remotely, helping you understand what your WBC levels may indicate and whether further testing or treatment is needed.

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Key takeaways

  • Sample required: Blood

  • Tests for: The number of white blood cells that help your body fight infection and inflammation

  • Healthy range: About 4,000–11,000 cells per microliter (µL) of blood (ranges vary by lab)

What can a WBC test tell you?

A WBC count helps show how well your immune system is functioning.

Too few or too many white blood cells can suggest infection, inflammation, or other medical conditions. 

Doctors use this test to:

  • Detect infections (bacterial, viral, or fungal)

  • Identify inflammatory or autoimmune conditions

  • Monitor bone marrow health and response to medication

  • Track the effects of chemotherapy or radiation

  • Investigate fatigue, fever, or unexplained illness

An elevated white blood cell count is called leukocytosis, and a low white blood cell count is called leukopenia. Because there are several types of white blood cells — like neutrophils, lymphocytes, and monocytes — results are often paired with a WBC differential to understand which cell types are changing and why.

What is being tested?

The WBC test measures your total count of white blood cells, which circulate in the bloodstream and help protect against infection and disease.

The main types of white blood cells are:

  • Neutrophils: Fight bacteria and inflammation

  • Lymphocytes: Target viruses and regulate immune memory

  • Monocytes: Clean up dead cells and respond to chronic infection

  • Eosinophils: Defend against parasites and respond to allergies

  • Basophils: Release histamine and aid immune signaling

A related test, called a white blood cell differential, shows how many of each type of white blood cell are present in your blood.

Changes in these cell types can affect your overall WBC count, helping providers pinpoint what’s happening in your immune system.

Where is the WBC test typically included?

WBC count is a standard part of the complete blood count (CBC), which evaluates overall blood and immune health.

The CBC also includes:

Providers may also order it before surgery, during illness, or to monitor chronic conditions and treatment effects.

Who should get a WBC test?

Most adults have a WBC test as part of routine wellness labs. Your provider may also recommend it if you:

  • Have symptoms of infection (fever, chills, or sore throat)

  • Experience inflammation or autoimmune conditions

  • Are receiving chemotherapy or immunosuppressant medications

  • Have a bone marrow disorder or unexplained fatigue

  • Are being monitored for chronic illness or recovery from infection

How Labs by Hers works

  • 1

    Book your test

    Schedule a lab draw in the Hers app at one of more than 2,000 convenient locations.

  • 2

    Get your results

    Review your lab results to understand which areas of your health may need attention.

  • 3

    Spot early signals

    Identify potential health risks or system imbalances before they become more serious.

  • 4

    Get your action plan

    Receive expert guidance tailored to your health profile and test results.

  • 5

    Improve over time

    Track your progress through a mid-year panel and ongoing provider check-ins.

Not available in all 50 states. Eligibility and provider order required. Lab results alone are not intended to diagnose, treat, or cure any condition. A provider will reach out about critical results and plans include access to 24/7 provider messaging.

Images for illustrative purposes only.

Frequently asked questions

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What can cause changes in white blood cell count?

WBC levels can rise with infections, inflammation, stress, smoking, or corticosteroid use. They can drop with viral infections, chemotherapy, autoimmune diseases, or vitamin B12/folate deficiencies.

What is a normal range for WBC?

A healthy range for WBC is about 4,000–11,000 cells per microliter (µL) of blood (ranges vary by lab)

Is a WBC test part of routine blood work?

Yes. It’s automatically included in a complete blood count (CBC), which is part of most annual checkups and diagnostic panels.

What are the screening recommendations for WBC?

WBC is commonly included in a complete blood count (CBC) to assess immune function and detect infection or inflammation.

Can stress or lifestyle affect WBC count?

Yes. Physical or emotional stress, smoking, and poor sleep can cause short-term increases, while chronic illness or nutritional deficiencies can lead to decreases.

Can a high or low WBC count mean I’m sick?

Not always. Temporary changes can happen from infection, medication, or stress. Persistent changes may require additional tests to find the cause.

How can I support healthy WBC levels?

A balanced diet, adequate sleep, stress management, and avoiding smoking help support immune health and normal blood counts. Does insurance cover this test?

Yes, because WBC count is included in the CBC — one of the most commonly covered lab panels. However, insurance is not required with lab testing through Hers.

What tests are related to this biomarker?

• Complete blood count (CBC)

• WBC differential

• Red blood cell count and hemoglobin

• Platelet count

• C-reactive protein (CRP)

• Erythrocyte sedimentation rate (ESR)

The information provided here is for informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always talk to a qualified healthcare provider about your specific health concerns.

Related biomarkers

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Basophils (absolute count)

Basophils are a type of white blood cell that help your body respond to allergens and fight certain parasites.

Learn more about Basophils (absolute count)

Basophils (percentage)

Basophils typically make up less than 1% of your total white blood cells and help trigger allergic responses and fight certain parasites. A healthy percentage means your blood contains the expected proportion of basophils, which are important for normal immune function.

Learn more about Basophils (percentage)

Eosinophils (absolute count)

Eosinophils are a type of white blood cell that help to control allergy-related inflammation and protect against certain parasites. A healthy count means your blood contains the expected number of eosinophils, which are important for normal immune function.

Learn more about Eosinophils (absolute count)

Eosinophils (percentage)

Eosinophils normally make up about 1-4% of your total white blood cells and help your body fight parasites and control allergy-related inflammation. A healthy percentage means your blood contains the expected proportion of eosinophils, which are important for normal immune function.

Learn more about Eosinophils (percentage)

Lymphocytes (absolute count)

Lymphocytes are a type of white blood cell that play a key role in building long-term immunity by recognizing and attacking viruses. A healthy count means your immune system is equipped to defend against infections and maintain balance.

Learn more about Lymphocytes (absolute count)

Lymphocytes (percentage)

Lymphocytes typically make up 20-40% of your total white blood cells and help your body fight viral infections while building long-term immunity. A healthy percentage means your blood contains the expected proportion of lymphocytes, which are important for normal immune function.

Learn more about Lymphocytes (percentage)

Monocytes (absolute count)

Monocytes are a type of white blood cell that help your body defend against bacteria and clean up damaged cells. A healthy count means your immune system is working efficiently to support your healing and protect against infection.

Learn more about Monocytes (absolute count)

Monocytes (percentage)

Monocytes typically make up about 2-8% of your total white blood cells. They act as your body’s clean-up crew to remove damaged cells and help fight bacterial infections. A healthy percentage means your blood contains the expected proportion of monocytes, which are important for normal immune function.

Learn more about Monocytes (percentage)

Neutrophils (absolute count)

Neutrophils are the most common type of white blood cell and act as your body’s first line of defense against bacterial infections. A healthy count means your immune system is well-prepared to respond quickly to infection when needed.

Learn more about Neutrophils (absolute count)

Neutrophils (percentage)

Neutrophils are the most common type of white blood cell, typically making up 50–70% of your total white blood cells. They act as your body’s first line of defense against bacterial infections. A healthy percentage means your blood contains the expected proportion of neutrophils, which are important for normal immune function.

Learn more about Neutrophils (percentage)

Systemic Immune-Inflammation Index (SII)

The systemic immune-inflammation index (SII) combines three key blood markers, platelets, neutrophils, and lymphocytes, to reflect the balance between inflammation and your immune defenses. A healthy SII means your immune system is well-regulated, not under excess inflammatory strain, and ready to defend your body against infection effectively.

Learn more about Systemic Immune-Inflammation Index (SII)

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Supporting references

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Reviewed by Felix Gussone, MD

Published 12/04/2025