Regardless of what you want to be - using your HS time to your advantage is worth it. And I applaud your passion at such a young age.
If your HS, offers an Intro to Healthcare class - then I would definitely sign up...
General advice:
1.Explore, try new things, join clubs/activities that sound even remotely something you could enjoy,/be passionate about. Does your HS offer a Medical Career Club, ASL Club? Hospital Volunteer Club? Does your HS have a career shadow day?
2. Any IB/AP classes that you can take during your HS career is a huge plus. By graduating HS with college credit, will give you lots of flexibility, regardless of your choice of major. Possibilities: graduate in less than 4 years, have a less rigorous schedule throughout your college career, be able to add minors, or go double major, study abroad, or change your major without extending past 4 years - and more importantly you save $.
3.Being fluent in any secondary language is a huge plus - especially Spanish and/or ASL.
4. In addition to the basic HS general credits of science, math, foreign language& English/Writing, some HS classes to considered: Bio 2 Chem 2, Physics, Anatomy; Statistics; Advanced Writing, Childhood Education classes, any upper division foreign language, Personal Finance, Psychology, Sociology. Depending on the level, you might gain college credit or at the very least give you a basic foundation of when you take it in college.
Most importantly enjoy your time in HS - college will bring on enough stress/life decisions. Use this time to explore your career aspirations.