100mg would certainly put almost anyone in the acceptable range but its more like a dose that a family doc would give. A real testosterone replacement therapy (TRT) doc would be shooting for the upper end. And if 100mg is putting you towards the upper end then you are probably making a fair amount of test on your own and thus dont really need TRT.
There are several factors we dont know here such as if this guy is self adminerstering or if hes getting it from a family or testosterone replacement therapy (TRT) doc, how old he is, if he cycles at all and if so how much because this plays into how shut down he is and how much natty test hes making.
first year i was on 150mg week and that along with my natty test was plenty as it was putting me around 1100. but now after a few cycles of tren, 150mg isnt cutting it anymore as im totally shut down and 150mg only gets me around 500 now. Had to bump it to 200mg