T Nation

Question about Half Life of Test Cyp


Have changed by protocol to 100mg, once per week (yes, I’m working on increasing frequency and lessening dose, etc as per advice).

My question is this: assuming a 7 day half life for test cyp, the amounts of testosterone in my system is going to top out around 200mg around week 7?

These would be the amounts of test in my system considering the accumulations of prior weeks shots/half lives with the current week’s 100mgs:

First week/first shot: 100mgs.
Second week : 150mg.
Third week: 175mg
Fourth week: 187.5mg
Fifth week: 193.75
Sixth week: 196.9mg.
Seventh week: 198.47


And here’s what my math says about my OLD protocol regarding 300mg every other week (assuming a 7 day half life:

Week one (first shot): 300mg
Week two: 150mg
Week three: 375mg
Week four: 187 mg
Week five: 393.5mg
Week six: 196.87mg
Week seven: 398.43 mg
Week eight: 199.17 mg.

Putting it out in math really shows the peaks and valleys, and obvious benefits of increasing frequency of injection with a lower amount


You’re overthinking way too much, just inject 50mg twice weekly and life will improve. You’re making the assumption that your half life is closer 7 days and not 5, then doing mathematical calculations based off an assumption.

Life is far too interesting for this to be. Math doesn’t = responds to testosterone, far too many biological variables.


I know. I’m just kinda playing around with the numbers. I like to see things that way.

I’m just hoping this lower dose of 100mg/week will be a better fit. I’m not quite sure whether I should wait 6 weeks and test e2 PRIOR to starting arimidex and see if I get a libido reaction, or whether I should just go ahead and low dose .25 e3d now. My e2 was 49 on the ultra sensitive test on the old protocol.

I receive the arimidex in the mail today.

I’ve had zero sex drive since about 20 years old.