When taking testosterone injections, when do we measure testosterone levels?

Timing of Testosterone Level Measurement with Injectable Testosterone

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

Initial Monitoring Timeline

• The first testosterone level should be measured 2-3 months after starting therapy or after any dose adjustment, as this allows sufficient time for steady-state levels to be achieved 1
• The first follow-up visit should occur at 1-2 months to assess clinical response and consider dose adjustments, though formal testosterone testing occurs at 2-3 months 1
• After the initial monitoring period, subsequent visits should be at 3-6 month intervals for the first year, then yearly thereafter 1

Understanding Injectable Testosterone Pharmacokinetics

The timing of blood draws is critical because injectable testosterone creates significant fluctuations in serum levels:

• Peak testosterone levels occur 2-5 days after intramuscular injection of cypionate or enanthate 1
• Levels return to baseline by 10-14 days post-injection 1
• This creates a "peaks and valleys" pattern that must be considered when interpreting results 2

Optimal Blood Draw Timing Based on Injection Schedule

For weekly injections:

• Measure at day 5-7 (midpoint) to assess average therapeutic levels 1

For biweekly injections (every 2 weeks):

• Measure at trough (just before next injection) to ensure levels don't drop below therapeutic range 1
• Alternatively, measure at midpoint (day 7) to assess mid-cycle levels 1

Critical pitfall: Measuring immediately after injection will show supraphysiological levels (mean 71 nmol/L or ~2050 ng/dL) that don't reflect average therapeutic exposure 3, while measuring too late may show artificially low levels.

Target Levels and Dose Adjustments

• Target testosterone levels should be in the mid-to-upper normal range (500-600 ng/dL) for optimal treatment response 2
• If levels are low-normal and clinical response is suboptimal, increase the dose 1
• Interpret all results based on the interval since the most recent injection, accounting for the specific formulation's pharmacokinetics 1

Additional Monitoring Parameters at Each Visit

Beyond testosterone levels, measure at each follow-up:

• Hematocrit/hemoglobin: Injectable testosterone causes the greatest increases in these parameters; intervention warranted if Hct >54% 2
• PSA levels (in men over 40): Measure at baseline and monitor during therapy 2
• Assess symptomatic response, voiding symptoms, and sleep apnea 1
• Perform digital rectal examination 1

Common pitfall: Injectable testosterone is associated with higher polycythemia risk compared to transdermal preparations 2, requiring vigilant hematocrit monitoring with potential dose reduction or temporary discontinuation if Hct exceeds 54% 2.