When I was in high school there's a biology topic, blood groups. During that period all the students were supposed to go to the laboratory and find out their blood groups on their own. According to the test, I turned out to be O+. I don't still know whether that's my real blood group or not because, I suspect there were some contamination and the instruments that were used weren't automatic like the ones in hospital but rather manual.
I understand blood group is very crucial especially during accidents it easen the work to the doctors and hence can easily be saved. I bet the only person in my home who knows their blood group is my mom. I don't know why we're so much reluctant on this issue but soon when I visit the hospital, I'll check out mine.