I have long been on the borderline on both weight and blood pressure for being able to give blood. There were regular blood drives at work, so one time I just decided to go for it to see what happened. I had successfully given a few years before when I was a bit heavier. This time, I only weighed around 105 but told them I weighed 110. Big mistake. They couldn't get enough blood out of me in the time limit, so the blood I did manage to donate (about 3/4 a bag) would have to be trashed. I had laid there for 45 minutes trying to give enough, and the needle was in kind of a painful position, so it was pretty miserable.

The requirements are there for a reason, and I learned my lesson at trying to get around them -- my intentions were good, but not worth it!