T Nation

Test Half-Life?


Hello all,

A question: Why is that standard T injection protocols (e.g., 50mg cypionate 2x/wk, EOD or E3D schedules, or even the old once-per-week routine) do not take into account the half-life of the ester (cypionate = 8 days per the FDA)?

Running this protocol thru a calculator shows that you are quickly jacking T beyond normal ranges. Theoretically, this is because when you inject dose #2, much of dose #1 is still in your system; when you inject #3, much of #2 as well as some of #1 are still in your system, and so on. So both the peaks and valleys of T levels continue to increase until stabilizing at levels that would probably too high for most of us, other than perhaps the guys who are 6'5" and 300 lbs.

On one hand, that would explain why many guys who stick to a consistent, moderate regimen start off feeling pretty good but eventually get out of balance again (the T levels indicated above would lead to nasty E2, and next thing you know you're adjusting your T and AI dose to try to feel good again, and then the wheels come off the wagon). This is what I've faced more than once -- don't change a thing, be careful and methodical, and still eventually feel steadily crappier.

On the other hand, real-life blood work seems not to bear out the model above.

In any case, there has to be a reason this is not really on the radar. Any input is most appreciated.


Yes, unless you front load (by doubling) the first week's dose, your T levels will continue increasing (but at a slower and slower rate) during the first weeks before stabilizing more or less after your 4th or 5th dose. It is this final stable level that matters. As long as your weekly dose is sane, this final target stable level will be fine.


There's a chart somewhere that shows serum T levels as the weeks progress. After the first few weeks, T levels off in the bloodstream - it doesn't continue to build, because your body metabolizes it (uses it up). You can probably google the chart if you want to investigate further.



Thanks for the reply.

But...according to the calculations, front-loading just starts the cycle from a higher plateau, causing super-high levels that much sooner.

It's only a theory, but I'm trying to figure out why, on my very stable and sane regimen...

  • Frontload 100 mg of cypionate, then 50mg 2x/wk
  • (Bloodwork 1.5 days after frontload: TT = 982 and E2 = 52, prior to starting AI)
  • Then added moderate liquid anastrozole EOD to tamp down E2

...I still end up, after 4 or 5 months, bogging down in the classic symptoms of low libido and ED. These symptoms have persisted for a couple months now, so I stopped everything 10 days ago. I'm allowing myself to crash to hormonal baseline so I can start over. I'd like for history not to repeat itself this time around.

(I don't have blood work to pin current levels down, regrettably. Also, I'm not using HCG.)


More than likely, your E2 is getting out of whack (that, along with your own natural T production bottoming out from the exogenous test). It is possible that you are letting E2 get too high, or too low (you could be an AI over-responder). It is very hard to tell the difference between the two for most folks. More blood work will help you figure out what is going on as you get several months into your routine. Usually recommend blood draws at 6 weeks after starting, then a month or so later, etc until you get dialed in. HCG will likely help, as well.


Thanks, catfish.

I agree that E2 must be out of whack. I'm trying to find the "why." But this is some complex stuff.

If anyone has a link to that serum T level chart , please share. The only charts I've seen are for a 14- or 21-day window, which aren't very instructive for the long-term outlook.


Because pinning every day, or even multiple times per day, would be a huge pain in the ass (literally)

And because a 2x/week protocol gives guys levels that are "level enough" for the most part



Much appreciated, VT.

I think I need to get bloodwork done more often. Otherwise it's like flying a plane with no functioning instruments in the cockpit, just a view of clouds thru the window.

Are the tests available at lef.org still a good option in everyone's view?


Not if you calculate the right way :slightly_smiling:

The half life is how long it takes for half the drug to be used up by your system, so assuming it is about a week for T-cyp, let's say you frontload by doubling the first week by injecting 200 mg and then continue by injecting 100 mg every week. Then

After injection #1 (200 mg), you have 200 mg in you, of which 100 mg is left after a week, so
after injection #2 (100 mg), you have 200 mg in you, of which 100 mg is left after a week, so
after injection #3 (100 mg), you have 200 mg in you, of which 100 mg is left after a week,

So you see that your T levels won't just grow and grow.

If you inject 100 mg every week and DON'T frontload, then

After injection #1, you have 100 mg in you, of which 50 mg is left after a week, so
after injection #2, you have 150 mg in you, of which 75 mg is left after a week, so
after injection #3, you have 175 mg in you, of which 87.5 mg is left after a week, so
after injection #4, you have 187.5 mg in you, of which 93.75 mg is left after a week, so
after injection #5, you have 193.75 mg in you, of which 96.875 mg is left after a week, so
after injection #6, you have 196.875 mg in you, of which 98.4375 mg is left after a week, so
after injection #7, you have 198.4375 mg in you, of which 99.218775 mg is left after a week, so
after injection #infinity, you have 200 mg in you, of which 100 mg is left after a week.

I think it should be clear from the above that you will approach slower and slower to the maximum of 200 mg in your body after injection. Technically it will take forever to get to that maximum, but in practice after about 5 weeks you are pretty much close enough.


Another way to think of it is that at once per week, you'll be at 50% at next injection. At twice per week, you'll be at 75% at next injection (assuming it clears at a linear rate). So for once per week you experience a 50% variation in max to min, but for twice per week you experience only a 25% variation in max to min - much less of a roller coaster.


Keep in mind, though, that a half-life of one week means:

  • after one week, 200mg is reduced to 100mg
  • after two weeks, that 100mg is reduced to 50mg
  • after three weeks, 50mg is reduced to 25mg


Also, very few folks on this board inject 1x/week. Any thoughts on how this applies to a 2x/wk or E3D injection scheme?


Yes, that is taken into account in the example calculations I showed above.

If someone injects more than once a week, the calculation is a bit more complicated, but the main result stands, which is that the levels stabilize after roughly 5 weeks. It doesn't keep building up to more and more.


You're over-thinking this. No need for a calculator. Bloodwork will tell the story. Test, tweak, test...... Testing is cheap through lef.org or Private MD Labs. Make sure you check T, Free T and E2. I'd aim for Free T and E2 in the low 20s. You can play around a little from there, but that should be a good starting point.

I've started to feel a lot better since moving to EOD injections and lowering my dose. I have really low SHBG, so frequent injections seem to work better. I also pay more attention to free T. If my total T was at your level, free T would be of the chart. E2 control is also critical for me.


Belated thanks, dhickey. I'm on board. I've re-started test after letting myself crash to baseline, and switched from liquid Adex to liquid exemestane. So far, exemestane is better for me, especially in the area of libido/erections, etc. I'm still dialing things in, but having some good days at this point, which I couldn't say a couple months ago. In the absence of bigger issues like thyroid, it seems like E2 control is the name of the game.


FDA data is not attempting to address optimal quality of life
FDA data is typically old and many recommendations predate disposable needles that enable self injections
do whatever works best for you, its your life