<p>I don't think you need a specific field...it's impossible to say as of now what your true passion is (and, probably, by the time you are leaving medical school to residency, you will still not be certain). So, I would urge you to do something fun and different...volunteering at and AIDS clinic is more meaningful for both student and admissions committee.</p>
<p>volunteering at a hospital won't really let you learn much about being a doctor...most places you just do busywork</p>
<p>try to get internships or shadowing oppurtunities, I got one in hematology and I was basically doing everything that the actual doctor was doing, ie. working with patient's blood, testing for leukemia (obviously re-checked by the doc) and other stuff...then you'll see if a job as an MD is right for you</p>