I would say that with your schedule including med school and serious training your gonna die out sooner or later. Sleep is very very important. When you study you will be using brain power. Same with your training. ITs gonna catch up to you. Your gonna hve to drop something, maybe the social life. lol. I once had two jobs while training. train 5am-8, 1st job 8-5, 2nd 6-11. sleep 11:30 to 4;30. After a week I would fall asleep at work. I ended up getting let go from the 2nd job. I just couldnt handle it. IMO 6 hours will not cut it. Serious athletes need 8 hours minimum. unless you can make up for those 6 hour days with power naps and a long sleep day during the week. Your gonna have to drop something.