I am 31 and upto now always had a heatlhy sex drive, in fact more than healthy. Off late I feel like I could probably go without it for weeks, I originally went the doctors for ED and got prescribed Viagra, although nothing in the blood tests shown anything in relation to diabetes or anything related to ED. I smoke, albeie 5 a day but I have cut back, and again I though this would only affect the bloof flow, not how I feel. I am also continiously tired, grumpy and irratable. Reading into it I could possibly suffer from a B12 defiency, was just after some advice?