Donating blood

They're holding a Blood Drive this week at the building where I work. It always makes me feel guilty to see the donors walking in and out, since I don't donate. I can't remember if I've ever actually been told I can't donate blood? It just seems like common sense though, since those of us with MVP already are prone to having a low blood-volume. We feel dizzy normally, so to donate blood would seem like we're literally giving away the very last drop.

But according to http://www.giveblood.org/index.php?page=faqs (click "I have a circulation or heart - related disorder, can I donate?"), as long as we are "stable," meaning we have not had chest pains in the past six months, we're ok to donate -- otherwise you need a physician's letter of approval. I'm assuming that means most of us would need to have a physician's letter of approval, because I don't know many of us who can go six months without chest pains.