Replying to Giving Blood and Drinking/Smoking

kinda browsed the other blood donation threads and didnt find an answer. noob question, but don't flame me.

so i'm donating blood at school tomorrow (friday) and there's a party planned for saturday night, so main question is, will i get really drunk and high off minimal quantities of alcohol and weed? and do they check your blood for weed or something like that? wouldnt want to tell my parents my blood got rejected because it tested positive for bud.