man... to be honest I'm 24 years old dude and I got a plethora of health problems that truly render me sterile.... and perhaps even dead by the time I'm 30..
At 21 you should consider your options bro. I'm not going to lie here. I happen to have met a really nice girl 2 months ago and we've been dating on and off and I dread the day I have to tell her I need to get tested for sperm count or perhaps vericocele surgery. It's not fair that I was born this way but shit happens. That's why I pin and pop shit. I honestly have been living in denial for sometime about this but I realized now I truly can't.
With that being said.. I know what good Anavar does to the body and you'll be happy with it but at 21 I can't imagine why you would need it.