John O'Connor
Member
You did show me that the most credible research found a half-life of about five days for testosterone cypionate. In addition, there have been a few instances of guys reporting two testosterone measurements in an injection cycle, and these have jibed with the five-day half-life figure. So yes, on a 3.5 day cycle there's usually going to be a pronounced trough, and the peak could be as much as 50-60% higher.
I also agree that serum testosterone peaks in the first 12 hours post-injection, and maybe much less. With propionate, at two to three hours post-injection I see quite high values, which are around the predicted peak. In modeling the pharmacokinetics of testosterone esters one finds that the major influence on time-to-peak is the half-life of pure testosterone in serum; time-to-peak is relatively insensitive to the half-life of the ester itself.
I stand corrected on the half life being attributed to the different oils used. Looks like it has more to do with the number of carbons attached to enanthate vs cypionate, being 7 and 8 carbons respectively. As for the peak timing for most of the sources seem to say its 48 to 72 hours for cypionate. Half-life of 8 days for cypionate is based on the manufacturer. Cataceous, if you have a study that shows cypionate peaks at 12 hours, I'd love to see it. There is a lot of contradictory information out there on the web. I did find a study suggesting cypionate peaks at 4-5 days, and lasts only 8 or 9 days, but that study is from 1987 and only had 11 participants. Unfortunately many other studies seem to reference it 2 to 3 decades later.
Madman mentioned enanthate and cypionate are basically interchangeable. I only have experience with cypionate, but while I've read enanthate has a 7 day half life and cypionate an 8 day half life, similar to the number of carbons attached to each, even Defy Medicals site says enanthate halflife is 4 to 5 days, and cypionate is 8. Just lots of contradictory information out there. Different types of injectable testosterone
Note I'm not claiming defy medicals website is correct or incorrect, just showing the contradictory information is everywhere.
On a personal note when I started TRT once weekly cypionate 100mg doses my trough on day 8 just prior to next injection was around 550 while my peak at 72 hours was 1100. Since changing to 3 injections per week my levels have been consistent no matter when my blood is drawn. Note If I know I'm having labs done tomorrow morning, but my next injection is tonight I will postpone it until after the blood draw as I do agree there is some initial spike immediately following injection. I attribute that to the oil not 100% absorbing into the muscle tissue upon injection. But that is just based on my personal experience as the first injection I ever took was 100mg in a single dose and within 2 hours my pupils were significantly dilated and I felt a huge rush of energy.