there is a lot missing here bro before anyone is going to try and give you advice. stats, cycle history, how long you been working out, and diet and training. I would say at 39 though trt would be a reasonable option but once you decide to go trt then you are pretty much there your whole life and need to be prepared for that. A lot of guys cruise at 125 a week of test E or test C. I guess the dose would be more dependent on the individual and how big you want to get. Hope this helps some man. If I were you I would find someone who is an actual trt patient and have been for some time and maybe talk to them on their thoughts of it as well.