Dear Prathiba,
    After passing the 12th Std, doing MBBS and subsequent Post Graduation courses in Medicine is by far the most widely tested as well as most effective pathway of building your career. In order to join MBBS you need to crack one of the entrance exams like NEET, AIIMS-UG, JIPMER-UG etc. depending on which college you're aiming to join.

If you have enough money, very good English skills, and tremendous motivation to study abroad, MCAT is a pathway available for you to get admitted to US medical colleges after 12th Std. Again , if you don't want to go to US right now i.e after 12th Std, you can complete your MBBS here and after that do your post gradation in US by taking the USMLE exam.