Stevie B at 2015-09-25 06:52:03:
I find the primary theme in this film to be attitudes towards other genders, races, sexual orientation etc. in this case sexual orientation.
Initially Ron States "I don't even know any faggots, I'm a rodeo". So even his interaction with homosexuals is extremely limited which is more than likely the cause of his ignorant attitude.
This develops throughout the film as Rons relationship with Rayon develops as does his amount of interaction/encounters with the gay community. This concludes in Ron providing free medicine to those affected (whereas in the beginning he was doing it to help himself and make money) and Rons transformation as a human being as he embraces Rayon which is symbolic of Rons acceptance of alternative lifestyles.
Running alongside this is the theory that the hospitals is supposed to be the place where you go for help whereas from Rons and Eves (overtime) perspective, the hospital is not necessarily helping people but doing what it can to get extra funding even if that's not necessarily in the interests of its patients. Ron on the other hand researches alternative forms of medicine and travels the world and manages to keep himself alive for a further seven years as opposed to the thirty days he was initially given.
In retrospect I think the main theme is about not judging a book by its cover, as Ron learns and experiences more about the gay community the more he becomes accepting of it. On the opposite side the more he learns about the medicine and hospitals/pharmaceutical companies as businesses the less trusting he is of them.
So I'd say the main theme is about knowledge being empowering and not judging or forming opinions on people/institutions from a position of ignorance.