Prednisone's Effect on White Blood Cell Count
Yes, prednisone does increase white blood cell (WBC) count, with elevations typically peaking at 48 hours after administration and showing a dose-dependent response. 1
Mechanism and Magnitude of WBC Increase
Prednisone causes leukocytosis primarily through:
- Increased release of neutrophils from bone marrow reserves
- Decreased migration of neutrophils from the circulation into tissues
- Reduced margination of neutrophils along vessel walls
The magnitude of WBC increase varies based on dosage:
- Low-dose prednisone: Mean increase of 0.3 × 10⁹/L
- Medium-dose prednisone: Mean increase of 1.7 × 10⁹/L
- High-dose prednisone: Mean increase of 4.84 × 10⁹/L 1
This leukocytosis can occur rapidly, with WBC counts potentially exceeding 20,000/mm³ as early as the first day of treatment and persisting throughout therapy 2.
Characteristics of Prednisone-Induced Leukocytosis
The WBC elevation from prednisone has several distinctive features:
- Predominantly affects polymorphonuclear cells (neutrophils)
- Often accompanied by monocytosis
- Typically causes eosinopenia
- Associated with variable lymphopenia 2
- Peaks within 48 hours after administration 1
- Maximum values typically reached within two weeks of starting therapy 2
Even small doses of prednisone administered over prolonged periods can induce significant and persistent leukocytosis 2.
Clinical Implications
Understanding prednisone's effect on WBC count is important for several reasons:
Differential diagnosis: When evaluating leukocytosis in patients on prednisone, clinicians must distinguish between steroid-induced increases and those caused by infection.
Infection monitoring: In patients on prednisone, WBC increases beyond the expected range (>4.84 × 10⁹/L after high-dose steroids) should prompt investigation for infection 1.
Diagnostic clues: Unlike infection-related leukocytosis, prednisone-induced WBC elevation rarely shows:
- Shift to the left (>6% band forms)
- Toxic granulation in neutrophils 2
Dose-Response Relationship
The relationship between prednisone dose and WBC response is complex:
- Higher doses generally produce greater leukocytosis
- WBC response to a given dose is reproducible in individual patients
- Response varies significantly between patients, independent of factors like age, renal function, or baseline WBC count 3
Timing Considerations
For accurate WBC assessment in patients on prednisone:
- WBC counts should be obtained before the morning steroid dose when possible 3
- Recognize that peak effect typically occurs around 48 hours after starting therapy 1
- In hospitalized patients not on steroids, WBC counts typically decrease during hospitalization, making steroid-induced increases more notable 1
Practical Applications
Prednisone-induced leukocytosis has been utilized clinically:
- As a method to measure bone marrow neutrophil reserve response
- For granulocyte mobilization (though less effective than G-CSF) 4
- Doses of 40-200 mg can increase neutrophil counts by approximately 4,000 cells/mm³ 5
When interpreting WBC counts in patients on prednisone, consider the timing, dose, and pattern of leukocytosis to distinguish between expected medication effects and potential infectious complications.