What gcses do you need to become a doctor?

Hi, I'm in year 8 and when i leave school i would like to be a doctor. I did want to become a barrister but i kept on changing my mind for what i wanted to do. However i have now decided that as i am getting to the end of year 8 i should just stick to one choose and doctor is what i will really love to do. The reason i am asking this questions is so i know what lessons i would need to take next year and what i will have to study for my gcses.