If you are interested in entering the field of medicine, why don't you try getting an internship in a clinic, hospital, pharmacy, vet clinic, etc...? Even volunteer work in a hospital, retirement home, etc.. would be good experience.
In terms of high school extracurricular activities, try joining the chemistry club, if there is one. Or any science-related club. See if there is any science experiment competitions that you can sign up for. Other than that, sign up for anything else that interests you. For example, debate club, drama club, etc... Do something that you enjoy, it will look good on an application anyway if there is a diverse balance of activities.