Just to throw in my five or six cents here. I wouldnt inject vitamins, simply because every time you poke yourself, you are creating scar tissue. do that for long enough and the scar tissue builds up, and it can be painfull. It might not be a huge deal, but vitamins are gonna need weekly/daily/monthly Injections?
not worth it IMO, you'll eventually get tired of poking yourself, then what are you gonna do when you actually want to inject something worth while?
I don't do this for my family, my friends, women, accolades, pride, or ego. I do it for me and no one else, its just part of who I am.