I've never noticed any decrease in my energy level. I don't tell the staff at the blood center that I plan to ride, because they will try to talk me out of it. Maybe I should listen, but so far, so good. It's interesting how different people have different results from donating.
I've also switched to donating platelets. They request that of frequent donors, because we've proven willingness to lie there and endure the discomfort. @
79pmooney, they have changed the method so now there is only one needle. There are alternating cycles of pulling and pushing of a few minutes each.