What is the optimal time to check testosterone levels in a male receiving testosterone injections (intramuscular testosterone) every two weeks?

From the Guidelines

The best time to check testosterone levels in a male receiving testosterone injections every two weeks is at the midpoint between injections, typically 7 days after the most recent injection, with blood drawn in the morning between 8 AM and 10 AM. This approach is supported by the need to assess testosterone levels when they are most representative of the average concentration throughout the treatment cycle, avoiding both peak and trough levels that can lead to inappropriate dosage adjustments 1.

Key Considerations for Testing

• Testing at the midpoint between injections helps in achieving a mid-normal testosterone value, which is crucial for maintaining the therapeutic benefits of testosterone replacement therapy while minimizing potential risks.
• Morning blood draws are preferred because natural testosterone levels are typically highest during this time, providing a more accurate baseline for comparison.
• Consistency in the timing of follow-up tests is essential to allow for meaningful comparisons and adjustments to the treatment regimen as needed.

Importance of Monitoring

Monitoring testosterone levels is critical for patients on testosterone replacement therapy to ensure that normal serum testosterone concentrations are being achieved and maintained. This involves testing 2 to 3 months after treatment initiation and/or after any dose change, with subsequent monitoring every 6 to 12 months once stable levels are confirmed 1. For patients receiving testosterone injections, measuring levels midway between injections is recommended, targeting a mid-normal value (500-600 ng/dL) 1.

Safety and Efficacy

While there have been concerns regarding the safety of testosterone therapy, including potential increased risks of cardiovascular events, the current consensus supports the use of testosterone in appropriately selected patients, emphasizing the importance of individualized treatment plans and ongoing monitoring to mitigate risks 1. The method of testosterone replacement should be tailored to each patient, considering factors such as personal preference, disease management skills, and potential side effects.

From the FDA Drug Label

Testosterone esters in oil injected intramuscularly are absorbed slowly from the lipid phase; thus, testosterone cypionate can be given at intervals of two to four weeks The half-life of testosterone cypionate when injected intramuscularly is approximately eight days.

The best time to check testosterone level in a male who is receiving testosterone injections every two weeks is just before the next injection, as this will provide a more accurate representation of the patient's trough levels. This is because the half-life of testosterone cypionate is approximately 8 days, and checking levels at this point will help to ensure that the patient's testosterone levels are within the desired range. 2

From the Research

Testosterone Level Check Timing

To determine the best time to check testosterone levels in a male receiving testosterone injections every two weeks, we need to consider the pharmacokinetics of testosterone and its fluctuations after injection.

• The study 3 suggests that traditional injectable testosterone esters generate supranormal testosterone levels shortly after injection, followed by a rapid decline, becoming subnormal in the days before the next injection.
• This fluctuation can be subjectively experienced as disagreeable and may not provide a stable testosterone level throughout the treatment period.
• In contrast, the study 4 compares the outcomes of hypogonadal men treated with intramuscular testosterone cypionate versus subcutaneous testosterone enanthate, showing that both treatments increase total testosterone levels, but subcutaneous testosterone enanthate has a lower testosterone peak-to-trough ratio.

Optimal Timing for Testosterone Level Check

Considering the fluctuations in testosterone levels after injection, it is essential to check testosterone levels at a time when the levels are stable and representative of the treatment's effectiveness.

• The study 5 uses daily subcutaneous testosterone for management of testosterone deficiency, which may provide a more stable testosterone level throughout the day.
• However, for traditional injectable testosterone esters, checking testosterone levels at the midpoint between injections (i.e., 1 week after injection) may provide a more accurate representation of the treatment's effectiveness, as levels are likely to be closer to the average level throughout the treatment period.
• The study 6 highlights the complex interactions between testosterone, dihydrotestosterone, and estradiol during testosterone replacement therapy, which may affect the free testosterone fraction and should be considered when assessing changes in testosterone levels.

Key Considerations

When checking testosterone levels in a male receiving testosterone injections every two weeks, consider the following:

• The timing of the testosterone level check in relation to the injection schedule
• The type of testosterone preparation used (e.g., traditional injectable testosterone esters or newer preparations like subcutaneous testosterone enanthate)
• The potential fluctuations in testosterone levels after injection and their impact on the accuracy of the testosterone level check 3, 4, 5, 6