For medical schools, the requirements may be different, but in general, you would need to take the GRE (Click here to read about the Graduate Record Examination
, a test of general knowledge). Many schools also require you to pass the TOEFL (Click here to read about the Test of English as a Foreign Language
). Although it may aggravate you, many graduate schools in the United States will require an applicant to successfully complete the TOEFL even though they come from an English-speaking country--it's a product of a bureaucratic mindset.
Those are two of the requirements of graduate schools in the United States. Once again, the requirements may be slightly different, or even radically different, for medical schools.