Quite a bit.
The required prerequisite courses for medical school are usually:
One year of Biology with Lab < A simplistic grasp of probability is needed>
One year of General Inorganic Chemistry with Lab < Algebra>
One year of Organic Chemistry with Lab < No math except in Lab>
One year of Physics with Lab < Algebra and Trig>
One year of College level math - Usually Calculus or some type of Trig or Statistics
Out of those:
General Inorganic Chem, O-Chem, Physics, and of course the math.
The only one that really requires any high level math is Physics. Chemistry is knowing the formulas and plugging in the numbers. Basically algebraic manipulation. In physics, you derive a lot of your formulas.