I'm 19 and I'm not gonna mess around with them. I'm not telling you what you can or can't do, it's your body, but it's definately a good idea to let your body finish growing, which usually happens in your mid 20's before you start screwing up your hormone levels because if your body is still growing and you begin messing around with them, they're probably not going to be correct when you're older. Examples: some things people experience is E.D. when taking these supplements at a young age, and infertility is definately a possible side effect if you're not taking your PH's the way they need to be taken and PCT correctly. What lifters our age need to do is eat right, protein, creatine, and some fish oils. Learn proper nutrition and exercise, then when you're older, if you decide to, research some ph's that fit you.