My father did this often while he was living, he had all the certificates from the old Red Cross blood service and stuff.
I on the other hand, have genetic hemochromatosis, for those that don't know it's the inability to process iron, found somewhat rarely in folks mostly of Celtic/Welsh, Western European ancestry. We are the Olympic champs of blood letting. In the 5 years since my diagnosis I've had more blood removed as therapeutic treatment for my disease then I care to think about. While before hand I was ambiguous about donating blood, now the thought of having it done when not required
, even though our blood can be highly useful due to it's overly rich iron content, nah, thanks, but no.