Total number of white blood cells that fight infection
20 of 22 providers
Complete Blood Count (CBC)
4.5-11.0 thousand/μL
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.
| Range Type | Level | Significance |
|---|---|---|
| Optimal | 5,000-7,500 /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-Normal | 7,500-11,000 /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. |
Bacterial infections:If WBC 11,000-25,000 with elevated neutrophils, evaluate for bacterial source (pneumonia, UTI, abscess, cellulitis). Antibiotics if indicated
Viral infections:Elevated lymphocytes suggest viral etiology (Epstein-Barr virus, CMV, influenza). Usually self-limiting;supportive care
Search for source:Physical exam, urinalysis, chest X-ray, blood cultures if febrile. Imaging if abscess suspected
Monitor response:WBC should normalize within days to weeks of treating infection. Persistent elevation requires further investigation
Sepsis management:WBC >20,000 with fever and organ dysfunction requires ICU-level care, broad-spectrum antibiotics, and source control
Anti-inflammatory diet:Mediterranean diet, omega-3 fatty acids (2-4g EPA+DHA daily), minimize processed foods and sugar. Can reduce WBC by 10-20%
Exercise:Regular moderate exercise (150 min/week) reduces chronic inflammation and WBC. Avoid overtraining which increases WBC
Smoking cessation:Smoking elevates WBC by 15-25%. WBC normalizes within months of quitting
Stress management:Chronic stress elevates cortisol and WBC. Meditation, yoga, adequate sleep (7-9 hours) reduce stress-related elevation
Treat underlying conditions:Rheumatoid arthritis, inflammatory bowel disease, chronic infections require disease-specific therapy
Weight loss:Obesity causes chronic inflammation. 5-10% weight loss reduces inflammatory markers and WBC
Identify cause:Check medications (chemotherapy, immunosuppressants, antibiotics), viral infections (HIV, hepatitis, EBV), autoimmune diseases (lupus), B12/folate deficiency
Stop causative medications:If drug-induced (e.g., carbimazole, sulfasalazine, clozapine), discontinue and recheck WBC. May take weeks to recover
Nutritional support:Ensure adequate B12 (>500 pg/mL), folate (>10 ng/mL), copper, zinc. Supplement if deficient
G-CSF (filgrastim):If severe neutropenia (<500) from chemotherapy or other causes. Stimulates bone marrow to produce neutrophils
Protect from infection:If WBC <1,500, avoid crowds, practice strict hand hygiene, consider prophylactic antibiotics. Any fever requires urgent evaluation
WBC differential and smear:Essential if WBC >15,000 without obvious infection. Look for blast cells (immature cells suggesting leukemia)
Acute leukemia:WBC often >50,000 with blasts on smear. Requires urgent hematology referral, bone marrow biopsy, chemotherapy
Chronic myeloid leukemia (CML):WBC often 50,000-500,000 with increased mature granulocytes. BCR-ABL gene testing diagnostic. Treated with tyrosine kinase inhibitors (imatinib)
Chronic lymphocytic leukemia (CLL):Gradual WBC increase (often 15,000-100,000) with mature lymphocytes. Often asymptomatic, may not require immediate treatment
Lymphoma:May cause moderate WBC elevation with atypical lymphocytes. Requires lymph node biopsy for diagnosis
Regular monitoring:Annual CBC for healthy adults. More frequent if on immunosuppressive medications or with known blood disorders
Avoid unnecessary medications:Many drugs can affect WBC (NSAIDs, certain antibiotics, antithyroid drugs). Use only when necessary
Infection prevention:Hand hygiene, vaccinations (flu, pneumococcal if immunosuppressed), safe food handling
Moderate exercise:Excessive intense exercise can temporarily elevate WBC. 30-60 min moderate activity most days is optimal
Hydration:Dehydration can falsely elevate WBC by concentration. Ensure adequate fluid intake
Timing considerations:WBC is higher in afternoon. For consistency, test at same time of day if monitoring trends
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.
Source:Madjid M, et al. Leukocyte count and coronary heart disease:implications for risk assessment. J Am Coll Cardiol. 2004;44(10):1945-1956.
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.
Source:Freifeld AG, et al. Clinical practice guideline for the use of antimicrobial agents in neutropenic patients with cancer. Clin Infect Dis. 2011;52(4):e56-e93.
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 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.
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.
| Provider | Includes | Annual Cost | Biomarkers |
|---|---|---|---|
 Superpower | ✓ | $199 | 100+ (150 with ratios) |
 WHOOP Advanced Labs | ✓ | $349 | 65 |
 Labcorp OnDemand | ✓ | $398 | 30+ |
| ✓ | $486 | 40+ | |
| ✓ | $468 | 83 | |
| ✓ | $349 | 100+ | |
 InsideTracker | ✓ | $680 | 54 |
 Function Health | ✓ | $365 | 100+ |
| ✓ | $250 | 65 | |
| ✓ | $495 | 70+ | |
| ✓ | $895 | 100+ | |
| ✓ | $1950 | 150+ | |
| — | $399 | 100+ | |
| — | $Varies | 75+ | |
| ✓ | $190 | 100+ | |
| ✓ | $99 | 50 | |
| — | $125 | 60 | |
| ✓ | $199 | 50 | |
| ✓ | $499 | 120+ | |
| ✓ | $4188 | 80+ | |
| ✓ | $375 | 85 | |
| ✓ | $700 | 129 |
20 providers include this biomarker in their panels
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs.
