I guess I should clarify before everyone gets up in arms.
http://forums.studentdoctor.net/showthread.php?t=985472
1) Who is the writer
2) What is your relationship with your writer
3) What can the writer vouch for
I have a hard time coming up with a situation where a doctor patient relationship is a good thing to base a letter of recommendation. Just a cautionary, most people think that their letters of rec are great and rarely are they right, they often confuse nice things being said about them with a strong letter. Just as most people think in a, "well, if I get a 4.0 from here on out, despite never coming close to that in the past, then XYZ will happen."