There is time in med school to lift. I have been working out for years now and would not give it up for medicine (though if I do make surg, we'll see if I have to).
I don't know if you are in for bulking, but if you are, here is what I did:
I did have time to go to the gym 5-6X a week, 1.5-2hrs (sometimes longer if I ate in between). During exams, I did not go, but this was bc I don't like to lift while stressed...I feel like I might slip up or something. Eating is the hard part, but you can buy protein bars for a good price (~$1.50 per bar of myoplex storm, no one eats these bc they are high in calories so they are on clearance). Tuna takes a minute to eat out of the can. Basically, if you are dedicated, you will have time.
Results: I am short (5'6") so bear that in mind (they say add 10lbs/"). Before school, I was in around 195 lbs, but went down to about 185-187 in school. Couldn't do much about this, but it was because my leg workouts took a hit. My bench went up significantly in school to 365 (from 335 pre med school). In short, there is time, and if I can do it, you can. It takes dedication and discipline. You would be surprised by how much more intensity you have when you work out...all that steam has to be vented somewhere.