White Blood Cells

What is White Blood Cells?

White blood cells (leukocytes) are the immune system's primary defense against infection, foreign invaders, and abnormal cells. The total WBC count represents five cell types: neutrophils (bacterial defense), lymphocytes (viral/adaptive immunity), monocytes (tissue macrophages), eosinophils (parasites/allergies), and basophils (allergic responses).

What might a high or low White Blood Cells mean?

Elevated WBC (leukocytosis) signals active infection, inflammation, stress response, or rarely leukemia. Low WBC (leukopenia) indicates immune suppression — increasing infection susceptibility. WBC is a PhenoAge biomarker: chronically elevated WBC predicts accelerated biological aging even within the normal range.

What is the typical reference range for White Blood Cells?

The general-population reference range shown here is 4 – 9 10x9/L. Reference ranges describe the general population and are not a personal target — discuss your results with your physician.

What can affect White Blood Cells?

It may be higher with: Bacterial infection (neutrophil-driven), Acute stress (cortisol mobilizes WBCs), Smoking (chronic low-grade elevation), Inflammation, Corticosteroid medications, Exercise (transient post-exercise leukocytosis), Leukemia and myeloproliferative disorders, Allergic reactions (eosinophil-driven). It may be lower with: Viral infections (often lower WBCs acutely), Bone marrow suppression (chemotherapy, radiation), Autoimmune diseases (lupus, rheumatoid arthritis), HIV/AIDS, Severe infections (sepsis can deplete WBCs), Medications (methotrexate, carbimazole), Aplastic anemia, Vitamin B12 or folate deficiency.