As we mentioned before, you can't best-guess medical translation. You either know the subject matter or you don't.
Depending on what type of medical translation you handle, it can be challenging to master so many different subjects. Thanks to the web, that is getting easier, at least in the areas of biology, chemistry, organic chemistry, and physics.
The Khan Academy, which has the stated aim to "empower everyone, everywhere with a free, world-class education" through videos, has a nice selection of videos in those four fields. Take a look and brush up on your know-how!
[Tip of the hat to The New York Times' DealBook]
ForeignExchange Translations provides specialized medical translation services to biopharma and medical equipment companies.