How Do I become a Medical Interpreter?

Hi all! I am just wondering if anybody has any experience with becoming a medical interpreter. I am about to graduate nursing school (5 more weeks!!!) and I will take boards this May or June. After I graduate, I would like to get certified as a medical interpreter so I can be paid for my skils. English is my second language, German in my first. Where do I go to get certified? Are there any national testing requirements? Any info would be great.