It depends on the transplant protocol the hospital uses. They can either take your marrow directly from your hip bone, and that is done under general anesthesia - so it's comparable to most minor surgeries. You'd be sore for a couple of days after. The other way is to "prime" your bone marrow to release stem cells into the blood stream (using drug -GCSF, is the one our center uses), and then removing blood directly from one arm - sending it through a machine to remove the stem cells, then putting the blood back into your other arm. It's similar to giving plasma, and it takes several hours. Biggest risk is getting leg cramps. Some transplant protocols prefer to use cells taken from the marrow, some from the arm (peripheral stem cells) - but there's not been shown to be a huge difference between the two sources for cancer patients (some other pediatric diseases, the doctors might prefer the cells come directly from donor marrow), and in most cases, if the donor really really prefers one way to donate over the other, they'll take it into account.
Originally Posted by moebius