I was on the bone marrow register, but sadly, I now have a blood disease and am more likely to need it than give it. Because of my not being able to donate, several friends and family members have added their names to the list in my stead. Two have donated. Others have gone for additional testing/matching.
Of the two who donated, they didn't have any ill effects. They were sore after the fact, but that's to be expected. I've had several marrow tests, which is like a mini sampling of the donor's ordeal. Your lower back/hip area will feel brused and sore for a bit, but knowing that you've given someone the chance at life will make your temporary pain and tenderness seem like nothing at all.
On a personal note, I would like to give a big thank you to you for concidering such a move. It is people who donate marrow, blood, organs and time who make little miricles happen all the time!!