Testosterone levels typically peak 1-3 days after an intramuscular injection, then gradually drop over the following weeks until the next injection. The rate of decrease depends on the dose and injection frequency.
- With typical injectable testosterone cypionate or enanthate doses of 100-200mg every 1-2 weeks, testosterone levels may drop by around 50% by the end of the second week after the injection.
- With more frequent dosage regimens such as 50-100mg every 3-5 days, the drop tends to be more gradual.
- Factors like age, BMI, and injection site can also impact absorption rates and declines between injections.
The timing of peak and trough levels after an injection, and the magnitude of
drop is quite variable between individuals. Monitoring trough levels via blood tests allows tailoring of the dosage regimen.
Key factors influencing testosterone level fluctuations:
- Injection frequency - More frequent injections lead to smaller drops between peaks. Weekly or twice-weekly injections create the most stable levels.
- Injection site - Gluteal injections lead to slower absorption and longer duration vs deltoid or thigh injections.
- Type of ester - Different esters release testosterone at different rates, influencing peaks and drops. Common esters:
- Cypionate and Enanthate - intermediate release
- Propionate - fast release
- Undecanoate - slow release
- BMI and body fat - Obese men tend to have lower peak levels, faster clearance and larger drops.
- Age - Clearance rates are slower with increasing age, leading to less fluctuation.
- Genetics & health conditions - Interindividual differences in absorption, transport and metabolism impact testosterone pharmacokinetics.
Monitoring trough blood levels and making dosage adjustments accordingly allows optimizing the regimen for stable levels. My clinic specializes in testosterone therapy management - Balance & Renew Clinic() offers convenient virtual consultations and blood testing.
As illustrated above, testosterone levels do not instantly plummet after an injection, but gradually drop over days-weeks depending on the dosage regimen. With typical every 2 week injections, levels may drop ~50% by the end of the second week. More frequent dosing creates smaller drops. Careful monitoring and dosage adjustments can minimize fluctuations.
