Hold off. If you're going to go to the trouble of getting an MBA, you may as well do it right.
There have been a lot of studies done about MBAs that found that less than stellar programs produce MBAs that do not pay for themselves. And most medical schools (though not all) are coupled with less than stellar MBA programs.
Also, MBAs without experience to back them up are not really worth a whole lot. You want to be able to integrate your professional knowledge into your studies. If you're looking to use an MBA to support your medical career, doing an MBA after you've had a bit of a medical career would make it a lot more valuable.
Look into executive MBA programs. With an MD in hand and a couple years of experience as a physician, you'd be an attractive candidate. Exec programs usually run one evening a week and every other Saturday or Sunday. You are expected to incorporate work done during your workweek into your MBA program. There are exec MBA programs offered by most of the top business schools now, and you can find a great program in most big cities.