I think I'd like to clarify this by stating that if you need to go to the GP to find out whether you are deficient in a vitamin is a tad silly, you go to a GP WHEN YOU ARE NOT WELL, he will decide whether you are deficient in something, more often than not its not a vitamin, more so a bad diet in general.
fuck, if bodybuilders aren't adding muscle or their tired all the time, there is either something wrong with their regimen or overall diet, usually too many poptarts, sugary drinks and not enough real food.