To correct two stated misconceptions above:
1) It is actually not easy at all to get into an MBA program. It is very difficult (unless the school is not a good one). Also, virtually all schools require the GMAT.
2) The business school side actually requires that applicants have *just as much* experience in the work force as straight business school applicants. That is why ppl who do the dual degree typically are much older and have had a wide medley of experiences in both medcine and business, often times career switchers
In any case, most schools that offer the dual degree require completely INDEPENDENT admissions processes at the med and business school. Admission/rejection into one does not help or influence the other. You are not treated as special; in fact, some med schools look down on applicants who have an interest in the business world. In any case, the two admisions committees do not even communicate with each other.
I know ppl who were admitted into one, but rejected by the other; and others who were vice versa. That is why simultaneous admission is so difficult and rare.