Why was my doctor surprised when i said my testosterone injections were now finally working (incredibly!)in week 5?

Depends on dosing: I don't know if you're getting "state of the art" dosing of im testosterone or not. Once a week is the bare minimum; twice a week is better.If your dose has been "every 2 - 3 weeks", it is entirely possible that because of the intermittent nature of your dosing, it has taken that long for your level to get into therapeutic range. A rule of thumb is 100 mg per week (50 mg 2x/wk) for nml guy.