White Blood Cells
Disclaimer: Information on this page is for educational purposes. Consult a physician to interpret your test results. Lissa Health helps track biomarker trends but does not replace medical advice.
What This Test Measures
White blood cells (leukocytes) are immune system cells that protect the body against infections, inflammation, and cancer. Their count in blood reflects immune system activity.
WBC is part of the Complete Blood Count (CBC) and helps detect bacterial and viral infections, inflammatory diseases, allergic reactions, and hematologic disorders. Both leukocytosis and leukopenia require evaluation alongside the differential count.
Physicians assess not only the total WBC count but also the proportion of neutrophils, lymphocytes, and other subtypes to refine the diagnosis.
Normal Ranges
| Group | Reference Range |
|---|---|
| Men | 4.0–9.0 × 10⁹/L |
| Women | 4.0–9.0 × 10⁹/L |
| Children | 5.0–13.0 × 10⁹/L (age-dependent) |
Reference ranges may vary by laboratory and assay method.
Causes of High Levels
- Acute and chronic bacterial infections
- Inflammatory diseases (rheumatoid arthritis, inflammatory bowel disease)
- Physical and emotional stress
- Corticosteroid therapy
- Leukemia and other hematologic malignancies
- Smoking
Causes of Low Levels
- Viral infections (influenza, COVID-19, HIV)
- Bone marrow suppression (aplastic anemia, chemotherapy)
- Autoimmune diseases
- Severe bacterial sepsis (consumption)
- Vitamin B12 or folate deficiency
- Splenomegaly (hypersplenism)
Test Preparation
- Blood can be drawn fasting or at any time — CBC typically requires no special preparation
- Inform your doctor about recent infections, medications, and chronic conditions
- Avoid strenuous exercise for 24 hours before the test
- Repeat testing may be needed after recovery from acute inflammation
Related Biomarkers
| Biomarker | Relationship |
|---|---|
| Neutrophils | Major fraction in bacterial infections |
| Lymphocytes | Elevated in viral infections |
| C-Reactive Protein (CRP) | Systemic inflammation marker |
FAQ
How often should I take this test?
Once yearly for routine checkups. During infections, chemotherapy, or immunodeficiency — as directed by your physician, often every 1–3 months.
What should I do if my result is abnormal?
Do not interpret the result in isolation. Consult your physician or hematologist for differential count evaluation and further testing if needed.
Last updated: June 2026