White Blood Cell Count (WBC)
White blood cells (leukocytes) are the soldiers of your immune system. They detect and destroy bacteria, viruses, fungi, and abnormal cells. A WBC count is part of every CBC and is one of the first indicators doctors check when infection or immune disorders are suspected.
Reference Ranges
Male
4.5 – 11
thousand/µL
Female
4.5 – 11
thousand/µL
Child
5 – 13
thousand/µL
Ages 6–12
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
Low WBC (leukopenia) weakens the immune system, making you more susceptible to infections. Causes include viral infections (HIV, hepatitis), bone marrow disorders, autoimmune conditions, chemotherapy, and certain medications.
What High Levels Mean
High WBC (leukocytosis) usually signals that your body is fighting an infection. Other causes include inflammation, allergic reactions, stress, smoking, and — less commonly — leukemia or other blood cancers.
Frequently Asked Questions
What is a dangerously high WBC count?
A count above 30,000/µL warrants urgent investigation. Counts above 100,000/µL (hyperleukocytosis) are a medical emergency, often associated with leukemia. However, even moderately high counts (12,000–20,000) during a known infection are usually expected.
Can stress raise WBC count?
Yes. Physical or emotional stress triggers cortisol release, which can temporarily increase WBC count. This is a normal response and usually resolves once the stressor is removed.
What are the types of white blood cells?
There are five main types: neutrophils (fight bacteria), lymphocytes (fight viruses, produce antibodies), monocytes (clean up dead cells), eosinophils (fight parasites, involved in allergies), and basophils (involved in allergic reactions). A differential count breaks down the percentages.
This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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