Just FYI nurse practitioners (NPs) can also diagnose/prescribe/refer. I happen to know this because my mom's finishing up school to become one. When she's finished, she'll get a huge pay bump, and have quite a few options open to her. A clinic at Walgreens, for example, is often staffed by a nurse practitioner. Cheaper than a doctor, but with their general prescriptive abilities.

http://en.wikipedia.org/wiki/Nurse_practitioner