IV Steroid-Induced White Blood Cell Count Increase
Intravenous steroids typically cause a white blood cell count increase of approximately 2.4-4.8 × 10⁹/L (2,400-4,800 cells/mm³) within 48 hours, with the magnitude directly related to the steroid dose administered.
Magnitude of WBC Increase by Dose
The degree of leukocytosis is dose-dependent 1:
- Low-dose steroids: Mean increase of 0.3 × 10⁹/L (300 cells/mm³) 1
- Medium-dose steroids: Mean increase of 1.7 × 10⁹/L (1,700 cells/mm³) 1
- High-dose steroids: Mean increase of 4.84 × 10⁹/L (4,840 cells/mm³) 1
The peak WBC response occurs at 48 hours after steroid administration 1.
Individual Variability
Important clinical caveat: Individual responses vary considerably, with increases ranging from -600 to +8,000 cells/mm³ after oral glucocorticoids 2. However, a given patient's WBC response to a specific steroid dose is reproducible when retested 2.
Cellular Composition of Leukocytosis
The steroid-induced leukocytosis is characterized by 2, 3:
- Predominantly neutrophilic: The increase is almost entirely due to segmented granulocytes (polymorphonuclear cells)
- Concurrent lymphopenia: Absolute lymphocyte count decreases, particularly CD4+ and CD8+ cells 4
- Monocytosis: Monocyte count increases 3
- Eosinopenia: Eosinophil count decreases 3
Time Course and Duration
- Onset: WBC increase can occur as early as 3 hours after oral steroid administration 2
- Peak: Maximum elevation at 48 hours for IV steroids 1
- Duration: With prolonged therapy, leukocytosis reaches maximal values within 2 weeks, then decreases but does not return to pretreatment levels 3
- Persistence: Even small doses of prednisone administered over prolonged periods can induce extreme and persistent leukocytosis 3
Clinical Interpretation Guidelines
When evaluating WBC counts after initiating steroids 1:
- Increases up to 4.84 × 10⁹/L within 48 hours after high-dose steroids are expected and likely steroid-induced
- Larger increases than 4.84 × 10⁹/L suggest other causes of leukocytosis (e.g., infection)
- Any increase after low-dose steroids should prompt investigation for alternative causes
- WBC counts >20,000/mm³ can occur as early as the first day of treatment and may persist throughout therapy 3
Distinguishing Steroid-Induced Leukocytosis from Infection
Critical differentiating features 3:
- Infection typically shows: >6% band forms (left shift) and toxic granulation
- Steroid-induced leukocytosis: Band forms and toxic granulation are rare
Practical recommendation: Obtain WBC and differential cell count before the morning steroid dose to avoid confounding interpretation 2.
Dose-Independent Effects on Lymphocyte Subsets
Notably, 1 mg/kg, 5 mg/kg, and 15 mg/kg methylprednisolone produce comparable effects on peripheral lymphocyte subsets, with a selective decrease in CD4+ and CD8+ cells at 6 hours that returns to baseline by 24 hours 4. This suggests that certain immunologic effects are not dose-dependent, even though total WBC increase is dose-related.