Whatever you do, don't tell them you had a routine colonoscopy. I was fine, nothing was wrong with me, there were no ill effects from it and I got a 6-month deferral just because. I guess honesty will get you nowhere. If I hadn't been honest I could still be donating. (I spoke with my own doctor and she couldn't understand a 6 month deferral either.)
Meanwhile I'm in the waiting area sitting next to a guy who smells like he just crawled out out of a dumpster filled with vodka and HE gets to donate. Okay....