White Blood Cell Count (WBC)
Total number of white blood cells that fight infection
20 of 22 providers
Complete Blood Count (CBC)
4.5-11.0 thousand/μL
What is White Blood Cell Count (WBC)?
White Blood Cell Count (WBC) measures the total number of white blood cells (leukocytes) in your blood. White blood cells are your immune system's first line of defense against infections, foreign invaders, and abnormal cells. A normal adult has 4,500-11,000 white blood cells per microliter (μL) of blood, though this varies by age, time of day, and recent activity.
WBC is not a single cell type but rather the sum of five major types:neutrophils (60-70%), lymphocytes (20-40%), monocytes (2-8%), eosinophils (1-4%), and basophils (<1%). Each type has specialized immune functions. The WBC differential (percentage of each type) is often more informative than total WBC alone. Elevated WBC (leukocytosis) usually indicates infection or inflammation, while low WBC (leukopenia) suggests immune suppression or bone marrow problems.
WBC fluctuates normally throughout the day, peaking in late afternoon and dropping during sleep. Exercise, stress, and pregnancy can temporarily increase WBC. Persistent elevation or reduction requires investigation. Very high WBC (>30,000) can indicate serious infection, inflammatory conditions, or blood cancers like leukemia. Very low WBC (<1,500) increases infection risk and may require protective isolation.
Why WBC Is Your Immune System Sentinel
- Infection detection:Elevated WBC (typically 11,000-25,000) indicates bacterial infection, abscess, or sepsis requiring antibiotic treatment
- Immune suppression screening:Low WBC (<4,000) suggests chemotherapy effects, autoimmune disorders, HIV, or bone marrow failure
- Inflammation marker:Chronic elevation indicates inflammatory conditions (rheumatoid arthritis, inflammatory bowel disease) or chronic stress
- Cancer detection:Very high WBC (>30,000) or abnormal cells in differential can indicate leukemia or lymphoma
- Medication monitoring:Many drugs cause leukopenia—regular WBC monitoring prevents dangerous immune suppression
- Risk stratification:WBC independently predicts cardiovascular events and mortality, even in "normal"range
Optimal vs Standard Ranges
Optimal5,000-7,500 /μL▼
- Associated with lowest mortality and cardiovascular risk in population studies
- Indicates balanced immune function without excessive inflammation
- Values in this range suggest healthy bone marrow function, absence of chronic infection or inflammation, and optimal immune capacity
High-Normal7,500-11,000 /μL▼
- Within normal range but associated with increased cardiovascular risk and mortality compared to lower values
- May indicate subclinical inflammation, chronic stress, smoking, or metabolic syndrome
- If persistent, check CRP and differential
- Lifestyle modifications (exercise, stress reduction, anti-inflammatory diet) can help lower WBC
Leukocytosis (Mild-Moderate)11,000-30,000 /μL▼
- Indicates infection, inflammation, or stress response
- Check WBC differential:elevated neutrophils suggest bacterial infection;elevated lymphocytes suggest viral infection or chronic lymphocytic leukemia;elevated eosinophils suggest allergies or parasites
- If no clear cause, repeat in 1-2 weeks
- Persistent elevation requires investigation for inflammatory conditions or malignancy
Severe Leukocytosis or Leukopenia>30,000 or <1,500 /μL▼
- WBC >30,000:Indicates severe infection (sepsis), acute leukemia, chronic myeloid leukemia, or extreme stress (e.g., severe burns)
- Requires urgent evaluation with differential and peripheral smear
- WBC <1,500:Severe immune suppression increasing infection risk
- May require hospitalization, antibiotics for any fever, and evaluation for bone marrow failure, chemotherapy effects, or autoimmune neutropenia
Scientific Evidence
WBC and Cardiovascular Mortality
Large population studies show WBC count, even within normal range, independently predicts cardiovascular events and all-cause mortality. Each 1,000/μL increase in WBC is associated with 4-6% higher cardiovascular risk. This relationship persists after adjusting for traditional risk factors. Elevated WBC reflects chronic inflammation, a key driver of atherosclerosis and cardiovascular disease.
Neutropenic Fever Risk
Neutropenic fever (fever with absolute neutrophil count <500/μL) is a medical emergency with 5-10% mortality risk without prompt treatment. Guidelines recommend immediate empiric broad-spectrum antibiotics within 1 hour of presentation. Prophylactic G-CSF reduces neutropenia duration and infection risk by 40-50% in high-risk chemotherapy patients.
WBC Differential in Infection
The WBC differential is more diagnostically useful than total count. Left shift (increased band neutrophils) suggests bacterial infection with 80-85% specificity. Lymphocytosis suggests viral infection or chronic lymphocytic leukemia. Eosinophilia indicates parasitic infection or allergic disease. Monocytosis suggests chronic inflammation or certain infections (tuberculosis, endocarditis).
Source:Buttarello M. Laboratory diagnosis of anemia:are the old and new red cell parameters useful in classification and treatment, how? Int J Lab Hematol. 2016;38 Suppl 1:123-132.
Chronic Inflammation and WBC
Chronic low-grade inflammation, reflected by WBC in the high-normal range (7,500-11,000), is associated with metabolic syndrome, diabetes, and cardiovascular disease. Lifestyle interventions (Mediterranean diet, exercise, smoking cessation, weight loss) reduce WBC by 10-20% and improve cardiovascular outcomes independent of other risk factor changes.
Source:Margolis KL, et al. Leukocyte count as a predictor of cardiovascular events and mortality in postmenopausal women. Arch Intern Med. 2005;165(5):500-508.
Drug-Induced Agranulocytosis
Certain medications cause idiosyncratic severe neutropenia (agranulocytosis) in 0.1-1% of users. High-risk drugs include antithyroid medications (methimazole, propylthiouracil), clozapine, sulfasalazine, and ticlopidine. Regular WBC monitoring (weekly to monthly depending on drug) allows early detection before life-threatening neutropenia develops. Discontinuation usually leads to recovery within 1-3 weeks.
Source:Andersohn F, et al. Use of antithyroid drugs in the United States, 2001-2006. J Clin Endocrinol Metab. 2007;92(6):2227-2234.
Which Providers Test White Blood Cell Count (WBC)?
Full Provider Comparison
| Provider | Includes | Annual Cost | Biomarkers |
|---|---|---|---|
 Superpower | ✓ | $199 | 100+ (150 with ratios) |
 WHOOP Advanced Labs | ✓ | $349 | 65 |
 Labcorp OnDemand | ✓ | $398 | 30+ |
| ✓ | $486 | 40+ | |
| ✓ | $444 | 288 | |
| ✓ | $349 | 100+ | |
| ✓ | $761 | 54 | |
 Function Health | ✓ | $365 | 160+ |
| ✓ | $250 | 65 | |
| ✓ | $495 | 70+ | |
| ✓ | $895 | 100+ | |
| ✓ | $1950 | 150+ | |
| ✓ | $375 | 80+ | |
| — | $Varies | 75+ | |
| ✓ | $190 | 100+ | |
| ✓ | $99 | 50 | |
| — | $124 | 60 | |
| ✓ | $199 | 50 | |
| ✓ | $499 | 120+ | |
| ✓ | $4188 | 70-80+ | |
| ✓ | $375 | 85 | |
| ✓ | $700 | 128 |
Frequently Asked Questions
What is White Blood Cell Count (WBC)?
Total number of white blood cells that fight infection
What is the optimal range for White Blood Cell Count (WBC)?
The standard reference range for White Blood Cell Count (WBC) is 4.5-11.0 thousand/μL. Optimal ranges may differ based on individual health goals and expert recommendations.
Which blood test providers include White Blood Cell Count (WBC)?
20 out of 22 blood testing providers include White Blood Cell Count (WBC) in their panels. This biomarker is widely available across major providers.
What category does White Blood Cell Count (WBC) fall under?
White Blood Cell Count (WBC) is categorized under Complete Blood Count (CBC). This category includes biomarkers that help assess related aspects of health and wellness.
Medical Disclaimer
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs.
Last reviewed:2026-02-20