there is nothing preventing/banning you from doing a 2nd residency in internal medicine. You might even get credit for some of your training in fp...though from what I have observe w/friends who switched residencies, etc., it's usually less than 1 year of credit that you get. A friend switched OB/Gyn to medicine after 1 year, and she got about 6 months credit, for example.
You don't say what year you are in residency. If you are a 2nd year, I'd start looking around for open spots in internal medicine. I don't see the point in finishing up 3 whole years of family practice if you aren't planning to practice in family practice.
If your current hospital has an internal medicine residency program, it might be worthwhile to talk to the program director of that, and ask him/her if they might have an open spot for the next year (either 2nd year or intern w/chance to be advanced/promoted to PGY2 early after 6 months or something). If he seems receptive, it might be time to talk to your family practice program director about your desire to switch specialties, but I wouldn't say anything until you have a plan and reasonable expectation that you have somewhere to go (either at your own hospital or some place else).
The residency program will only get 1/2 funding for you if you are doing a year 4,5 and 6 as a medicine resident. If you skipped your 3rd year of famly practice and went to medicine, my understanding is the new program would get full funding (for that 1 year/1st year that you do there). This is my understanding of the way Medicare funding is done, at least.
