Can a steroid (corticosteroid) injection, such as triamcinolone (triamcinolone) or methylprednisolone (methylprednisolone), in the shoulder cause leukocytosis (elevated white blood cell count) in a patient with a history of shoulder pain or inflammation?

Can a Steroid Shot in the Shoulder Cause Elevated WBC 14?

Yes, a corticosteroid injection in the shoulder can absolutely cause an elevated WBC count of 14 × 10⁹/L, and this is a well-established, dose-dependent effect that peaks at 48 hours post-injection. 1

Mechanism and Expected Magnitude of Leukocytosis

Corticosteroids are lymphocyte-depleting agents that cause a predominantly neutrophilic leukocytosis, which can occur as early as the first day of treatment and persist throughout therapy. 1 The mechanism involves:

• Neutrophil demargination and increased bone marrow release leading to elevated neutrophil counts 1
• Lymphocyte depletion occurring simultaneously 1
• Dose-dependent response with higher doses producing greater WBC elevations 2

Expected WBC Elevation After Shoulder Injection

For a typical shoulder injection (which usually contains 40-80 mg of methylprednisolone or triamcinolone):

• Peak effect occurs at 48 hours post-injection 2
• Medium-dose steroids (equivalent to what's used in shoulder injections) produce a mean increase of 1.7 × 10⁹/L WBCs 2
• High-dose steroids can produce increases up to 4.84 × 10⁹/L WBCs within 48 hours 2
• Individual variation is significant, with responses ranging from -600 to +8,000 cells/mm³ in some studies 3

A WBC of 14 × 10⁹/L after a shoulder steroid injection is entirely consistent with the expected steroid effect and does not automatically indicate infection. 2

Critical Decision Point: Distinguishing Steroid Effect from Infection

The American College of Physicians provides specific guidance on when to investigate for infection versus attributing leukocytosis to steroids:

• Investigate for infection if WBC >14,000/mm³ AND left shift present (>6% bands), regardless of steroid dose 1
• Check the peripheral smear for left shift and toxic granulation to distinguish infection from steroid effect 1
• Consider the magnitude of increase: Increases larger than 4.84 × 10⁹/L after high-dose steroids, or any significant increase after low-dose steroids, suggest other causes of leukocytosis 2
• Assess clinical context: Fever, wound erythema, purulent drainage, or systemic symptoms increase suspicion for infection 1

Practical Algorithm for WBC 14 After Shoulder Injection

If WBC = 14 × 10⁹/L within 48 hours of shoulder steroid injection:

1. Order CBC with differential to assess for left shift 1

   • If bands >6%: Investigate for infection regardless of total WBC 1
   • If bands ≤6%: Likely steroid effect, monitor clinically 1

2. Assess clinical signs of infection 1:

   • Fever, shoulder warmth, erythema, purulent drainage
   • Systemic symptoms (rigors, hypotension)
   • If present: Pursue infection workup (aspiration, cultures, imaging)
   • If absent: Attribute to steroid effect

3. Consider timing 2:

   • Within 48 hours of injection: Most consistent with steroid effect
   • Beyond 72 hours with rising WBC: Consider alternative causes

Important Caveats

• Steroid-induced leukocytosis can mask infection in immunosuppressed patients, making diagnosis more challenging 1
• Serial WBC monitoring with differential is necessary if infection is suspected, rather than relying on a single elevated value 1
• The exact WBC threshold at which bleeding or infection risk increases is not precisely known, requiring clinical judgment 4
• Even small doses of prednisone over prolonged periods can induce extreme and persistent leukocytosis, though a single shoulder injection is typically a one-time moderate dose 1

When to Worry About Infection Despite Steroid Use

Specific red flags that should prompt infection investigation even if WBC elevation could be steroid-related:

• WBC >14,000/mm³ with left shift (>6% bands) 1
• WBC increase exceeding 5 × 10⁹/L from baseline 5
• Progressive WBC elevation beyond 48-72 hours post-injection 2
• Clinical signs of infection (fever, local warmth, erythema, purulent drainage) 1
• Repeated intra-articular steroid injections (predisposing factor for joint infection) 4

In summary, a WBC of 14 × 10⁹/L after a shoulder steroid injection is most likely due to the steroid effect itself, but requires assessment of the differential count (specifically bands) and clinical context to confidently exclude infection. 1, 2