I don't have a clue - keep meaning to find out. I went ot give blood a few years ago at Uni when the big white van turned up. Had to give and go to class after waiting for over an hour to get seen. Was a busy day I can tell you.
I have been told by my Doc that I should give blood as mine appears think and good (!!)
I have been told by my Doc that I should give blood as mine appears think and good (!!)