Right. And I quickly learned never to donate, then go to work. I was usually on the line for the min required iron levels, and I often required 20-30 mins recovery time. If the ambient temp was cool, mid 60's or less, I was fine, but if it was warmer than that, I'd feel light headed for up to an hour later.

BTW, good for you for donating blood. I believe that there's often a shortage, especially of the rarer types like you have.