Most schools tend not to allow students to defer unless they have a Rhodes, Fulbright, Marshall, Scholarship, Peace Corps or military commitment, meaningful research (i.e. NIH funded), or a very very good reason to explain why you can't possibly go to med school this year. Basically you're indicating that you werent really serious about applying to med school while many others would kill for your spot. Schools don't like it. But you never know, ask the admissions office.