There are at least two doctors on this forum. Myself, a pediatrician, and a dermatologist. I can't remember her name. There may be others who have chosen not to identify themselves as such. It takes good grades to get into medical school but it also takes persistance. Many people who don't get in the first time give up. If that is really what you want to do then keep trying, the effort is noted by admission committees. And no, I don't have much time to practice. Short pieces are not much of a problem but anything substantial like a Beethoven sonata is problematic in that by the time I have one movement learned any previous movements have fallen apart. But I play for fun only, noone else ever hears me.
Hi, the dermatologist is me, Teresa. Drjames is absolutely right about persistence. You do need grades, but that is not the only criterion. It's good if you've shown some initiative--for example, worked in a medical research lab, volunteered in a free clinic, etc. Also, being well-rounded sounds like a cliche, but your musical studies can help. Many years ago I interviewed for med school with a Johns Hopkins representative who was visiting my own campus. I happened to be coming straight from my piano class, and had an armful of piano literature. The interviewer talked to me the whole time about music, and I was accepted to Johns Hopkins. (Didn't go there for other reasons, but it was a nice feather in my cap.)
Practice time for me is a toughie, too. Usually I do some in the mornings and more on weekends. I have played 4 Mozart concertos with chamber orchestra, but I have to say, I worked on each one for over a year before performing it, and used score on a couple of them because I was unsure of my memory.
If you love medicine, go for it--but ONLY if you love it, because the work required to get in is nothing compared to the work you will face for the next 8 years or so (Not to mention the rest of your life!)
Teresa