What should I do if I have leukocytosis (elevated white blood cell count)?

Management of Elevated White Blood Cell Count (Leukocytosis)

An elevated white blood cell count (leukocytosis) requires a systematic evaluation for underlying causes, with bacterial infection being the most common serious etiology requiring prompt assessment and treatment. 1, 2

Initial Assessment

• A complete blood cell count with differential should be performed for all patients with suspected leukocytosis to determine the severity and type of elevation 1, 2
• An elevated WBC count >14,000 cells/mm³ or a left shift (band neutrophils ≥16% or total band neutrophil count ≥1,500/mm³) strongly indicates bacterial infection (likelihood ratio 3.7) and requires careful assessment even without fever 1, 2, 3
• Evaluate for common sources of infection including respiratory, urinary tract, skin/soft tissue, and gastrointestinal systems 2, 3
• Consider non-infectious causes of leukocytosis including:
  • Medications (corticosteroids, lithium, beta-agonists) 4
  • Physical or emotional stress 4
  • Chronic inflammatory conditions 2, 4
  • Smoking and obesity 5

Management Based on WBC Count Severity

Mild to Moderate Leukocytosis (11,000-30,000/mm³)

• Perform targeted diagnostic tests based on suspected infection site:
  • Urinalysis and culture for urinary symptoms 3
  • Blood cultures for systemic symptoms 2, 3
  • Respiratory evaluation for respiratory symptoms 3
• Monitor for signs of systemic infection that would require antimicrobial therapy 2

Severe Leukocytosis (>30,000/mm³)

• Consider hematologic malignancy, especially with concurrent abnormalities in red blood cell or platelet counts 4
• Look for symptoms suggestive of hematologic malignancy: fever, weight loss, bruising, fatigue, lymphadenopathy, or hepatosplenomegaly 5, 4
• Consider referral to hematologist/oncologist if malignancy cannot be excluded 5, 6

Hyperleukocytosis (>100,000/mm³)

• Treat as a medical emergency due to risk of brain infarction and hemorrhage 4
• Initiate intravenous hyperhydration (2.5-3 liters/m²/day) 1
• Consider cytoreductive therapy:
  • Hydroxyurea (25-50 mg/kg/day in 2-3 divided doses) for asymptomatic patients 1
  • Leukapheresis or exchange transfusion for emergency organ-threatening conditions like cerebral or pulmonary leukostasis 1

Special Considerations

• Avoid dismissing leukocytosis in the absence of fever - bacterial infection can present with leukocytosis alone 2
• In children with chronic myeloid leukemia presenting with hyperleukocytosis, leukostasis is usually observed at much higher WBC counts than 100 × 10⁹/L 1
• Avoid invasive procedures while active infection is present 7
• Monitor WBC count to ensure resolution if infection was identified 2

Follow-up Recommendations

• If infection is diagnosed and treated, repeat CBC to confirm normalization of WBC count 2
• If initial evaluation is negative but leukocytosis persists, consider referral to hematology for further evaluation 6
• Acute leukemias require urgent referral to a hematology specialist due to potential life-threatening complications 6