I haven't donated blood in a while because I have this wierd fear that they will test the blood and it will come up THC-positive. I know it's ridiculous to worry about shit like that, but I do it anyways. Good to know they don't test for weed. I also usually have to cancel right on the day I'm about to donate because I'm sick (or will be having major dental work... it always coincides).
Next time I donate I am totally getting high right afterwards.