You do not have to do a post bacc though it is advisable. I know of a student who just took the required course work on her own and is now in medical school. But a postbacc is good. Esp if they have a linkage porgram with a medical school and provide a good environment. Serveral good ones are Columbia, Bryn Mawr, and NYU check out the AAMC website for more info search post baccs