How long after a testosterone (intramuscular injection) shot should a patient's testosterone levels be re-tested?

Timing of Testosterone Level Testing After Intramuscular Injection

For standard testosterone cypionate or enanthate injections, measure testosterone levels midway between injections (typically day 5-7 for weekly injections or day 3-5 for biweekly injections) at 2-3 months after treatment initiation or any dose change. 1, 2

Initial Monitoring Timeline

• The first testosterone level should be checked 2-3 months after starting therapy or after any dose adjustment, as this allows sufficient time for steady-state levels to be achieved 1, 2
• Schedule the first follow-up visit at 1-2 months to assess clinical response and symptom improvement, though formal laboratory testing occurs at 2-3 months 1, 2
• After confirming stable levels on a given dose, subsequent monitoring can be performed every 6-12 months 2
• During the first year, monitoring visits should occur at 3-6 month intervals, then yearly thereafter 1

Pharmacokinetic Considerations for Timing

Understanding the pharmacokinetics of injectable testosterone is critical for accurate interpretation:

• Peak serum testosterone levels occur 2-5 days after intramuscular injection of testosterone cypionate or enanthate 1, 2
• Testosterone levels return to baseline by 10-14 days post-injection 1, 2
• The half-life of testosterone cypionate is approximately 8 days 3
• Injectable testosterone creates fluctuating levels with peaks and valleys between injections, which must be considered when interpreting results 1, 2

Optimal Blood Draw Timing

To accurately assess treatment efficacy, blood should be drawn midway between injections:

• For weekly injections: draw blood on day 5-7 1
• For biweekly injections: draw blood on day 7-10 1, 2
• Avoid drawing blood at peak (days 2-5) or trough (days 10-14) to prevent misleading results 1, 2
• The target when measured midway should be in the mid-to-upper normal range 1, 2

Dose Adjustment Strategy

• If clinical response is suboptimal and midpoint testosterone levels are in the low-normal range, increase the dose 1, 2
• Recheck testosterone levels 2-3 months after any dose change 1, 2
• Target testosterone levels in the mid-to-upper normal range for optimal treatment response 1

Additional Monitoring Parameters

Beyond testosterone levels, comprehensive monitoring should include:

• Hematocrit or hemoglobin at each visit; if hematocrit rises above reference range, consider temporarily withholding therapy, reducing dose, or performing phlebotomy 1, 2
• PSA levels at baseline and during follow-up visits 1
• Assessment of symptomatic response, voiding symptoms, and sleep apnea 1
• Digital rectal examination 1

Common Pitfalls to Avoid

• Do not draw blood immediately before the next injection (trough levels), as this will underestimate average testosterone exposure and may lead to unnecessary dose escalation 1, 2
• Do not draw blood 2-3 days after injection (peak levels), as supraphysiological levels may prompt inappropriate dose reduction 1, 2
• Ensure all testosterone measurements use the same assay, preferably at the same laboratory, for consistency 1
• Do not measure testosterone levels during recovery from GnRH agonist therapy, as testosterone may not return to normal for a median of 16.6 weeks after discontinuation 1