Will I have to take lower division Math classes after changing my major?

Pre-med can be done with any major, but specific pre-med courses need to be taken (though the list does vary by medical school).

Many, but not all, medical schools require calculus and/or statistics (courses suitable for science majors, though not necessarily the hardest ones that math and statistics majors take).

You will likely have to take a math placement test to place into the math sequence leading to calculus. To get an idea of what may be tested, you may want to try these quizzes: http://www.math.buffalo.edu/rur_index.html .