The reason I can't donate blood is the silliest ever. I wanted to give blood so I went to a blood collection place. They tried to take my blood for 15 minutes but couldn't because... my veins are too small for their needles! Apparently, in order to draw a worthwhile quantity of blood from you, they use bigger needles than what they would use for say, a blood test. And my veins are really tiny. So they can't take my blood. I am gutted because I really want to!