From the Guidelines
When monitoring testosterone levels during testosterone replacement therapy (TRT) with injections every 2 weeks, blood tests should be done at the trough level, which is immediately before your next scheduled injection. This approach is based on the principle of ensuring that the lowest testosterone level in the cycle remains within the therapeutic range, as supported by the concept of monitoring testosterone levels to determine that normal serum testosterone concentrations are being achieved 1. The timing of testosterone measurements will vary depending on the preparation, and for patients receiving testosterone injections, levels should be measured midway between injections, targeting a mid-normal value (500-600 ng/dL) 1. However, in the context of every 2-week injections, this translates to testing immediately before the next injection, which is typically 12-14 days after the previous injection. Key points to consider when monitoring testosterone levels include:
- Trough measurements are preferred because they reveal whether your minimum testosterone levels remain within therapeutic range throughout your treatment cycle.
- If your trough levels are adequate, your peak levels will almost certainly be sufficient.
- Your healthcare provider may occasionally request both trough and peak (1-2 days post-injection) measurements to understand your full testosterone profile, especially when adjusting dosages.
- Consistency in the timing of your blood draws relative to your injection schedule is crucial to ensure comparable results across different tests, allowing for more accurate dose adjustments if needed. It's also important to note that the method of testosterone replacement should be individualized for each patient, and transdermal testosterone preparations are often suggested for most hypogonadal men because they usually produce normal serum testosterone concentrations, and patients typically find them the most convenient 1. However, for patients on injectable testosterone, monitoring at the trough level every 2 weeks is a practical approach to ensure therapeutic levels are maintained.
From the Research
Testosterone Level Monitoring on TRT
- The frequency of monitoring testosterone levels while on Testosterone Replacement Therapy (TRT) can vary, but it is generally recommended to check levels every 2-3 weeks for injectable formulations 2, 3.
- For injectable testosterone, it is common to check trough levels, which are the lowest levels of testosterone in the blood, usually just before the next injection 4, 3.
- Trough levels are typically checked to ensure that testosterone levels do not drop too low, which can cause symptoms of hypogonadism to return 5.
- The goal of TRT is to maintain testosterone levels within the physiological range, and monitoring trough levels can help adjust the dosage and frequency of injections as needed 2, 4.
- Different formulations of testosterone, such as transdermal gels or nasal sprays, may have different monitoring schedules, and it is essential to follow the specific guidelines for each formulation 5, 6.