I am an international student, and I will be taking Math Level 2 and Biology M in October. I am going to be studying molecular biology. The reason I am taking math level 2 is to make up for the OK math results on my transcript (our school math is much harder than the math tested on the sat 2 so i think I have a very good shot). Do you think taking chemistry would also be a good idea? I am planning to apply to top colleges. I know that doing well on all three tests would be great for me. Is taking chemistry relevant for my field of study, or will it just take away focus and attention from the other two (I am aiming for a really high score)?
I don't think you should bother taking the Chemistry SAT II. There are very few schools that ask for three subject tests, and if you feel confident about your scores on Biology and Math, there's no need to burden yourself with an additional exam.
For reference, here's a list of colleges that recommend or require subject tests (along with their specific policies). Almost all of these schools only ask for two subject tests, which you already have covered with Math and Biology. If you still want to take a third subject test (this might be the case if you're applying to Georgetown, the one university that highly recommends sending in three SAT II scores), I'd suggest something in the humanities like Literature or World History so you can demonstrate your skills in a more diverse group of subjects.