Am I understanding half-life correctly?


New Member
I'm trying to gain better insight into how various protocols affect the rate at which T. Cyp. builds up in the system (e.g., weekly vs. 3x week vs. daily). My understanding is that the half-life of T. Cyp. is 8 days. So if you inject 100mg on Day 1, there is approximately 50mg remaining in your system on Day 8. Then, on Day 16, you'll have 25mg remaining (one half of 50). And so on. If you're injecting more frequently than every 8 days, then the total amount of T Cyp in your system is the sum of current injection + remaining amount from previous injections. Good so far?

I mapped out what I think 18mg/daily would look like, in terms of initial buildup. Here's what I came up with:

And here's the calcs:

My question for the forum is this: Am I understanding half-life correctly? Can I assume that T Cyp is building in my body roughly at this rate if I inject 18mg daily?


Super Moderator
You have the right idea, except the half-life of testosterone cypionate is more like five days. Compare what you're doing to this site, which has the right numbers and plots the results:


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