I faced a similar dilemma when I was leaving school and was interested in pursuing a career in writing and communications but ended up working in Sales at a pharmaceutical company. I thought I had settled only to find out that there were enormous opportunities in combining my writing skills with my growing expertise in the healthcare industry. Now a few years later, I work in corporate communications at my company and I spend most days writing patient and health information stories. I absolutely enjoy it but kind of stumbled into it.
It doesn't have to be this way for you. There are so many websites and companies looking for writers to tell health and wellness stories. Start there. Read WebMD and similar websites to get a sense of the writing style and what the kind of stories that they tell. Then write about a topic that is important to you, it can be anything from a friend's cancer diagnosis, your workout regimen or an interesting science fact that you learned in school.
After completing this exercise, you can gage your passion and enthusiasm for writing about health topics and if you are still interested in pursuing a career in communications and health sciences, look for copywriting or writing positions at health care agencies, hospitals, pharma companies and others. Don't get discouraged if you don't land anything at first, keep building your writing portfolio and writing style through freelance opportunities or internships.
Please let me know if this helps.
P.S. Check out www.pfizer365.com to see examples of patient stories and health information.