There is no required major that you must take up in order to be granted acceptance into medical school. You could even major in History if you wished to do so. What matters is that you focus a good amount of science and math. You know, Biology, Chemistry, Physiology, Physics, etc. and College Algebra, Statistics, Calculus, etc. A lot of students choose to major in Biochemistry since it includes all of those important components which relate directly to medical school.