Hi Venkat,
Welcome aboard,Believe me when i say that you have no need to worry about anything,just keep your blood counts in check,you have an exceptionally good hb level for a minor, i am also a minor and i've never seen my hb any further then 11,going to gym won't effect your hb,instead it will give you more strength and sense of fitness as in any normal person's case,and thal minor can't be and won't be life threatning if you hb is that persistent.
ONLY THING YOU HAVE TO WORRY ABOUT RIGHT NOW IS GETTING YOUR WIFE TESTED FOR THAL TRAIT,BECAUSE IF SHE HAS THAL TRAIT,THERE IS A 25% CHANCE THAT YOU CAN HAVE A THAL MAJOR BABY,WHENEVER YOU PLAN TO HAVE A BABY,AND THAL MAJOR NOW A DAYS IS MANAGEABLE,BUT IT CAN BE LIFE THREATNING,SO IT'S BETTER NOT TO HAVE YOUR CHILD GO THROUGH IT.
regards,
ZAINI.