When choosing your letter of recommendations, you do not want to choose letters all from doctors.  The same premise holds true for getting all letters from your class professors. At a very minimum you want to have one letter from a physician and at most two.  Do not have more than two.  You want to have other letters from your community service activities or from your research mentor.  

The goal of the letters is to add extra dimensions to your application.  You want to have each letter comment on a particular key aspect of your personality or your interests.  For example, a letter from a physician can comment on your patient interaction skills and maybe your skills in taking a complete history of present illness.  A letter from your research mentor could potentially comment on you inquisitive nature, work ethic, and independence in lab.  A letter from a director from a community service organization like Habitats for Humanities can attest to your volunteerism and team work in helping build houses etc.  Lastly, to round things off with the letters of recommendations, you should get a letter from a professor that taught you in undergraduate and who you visited frequently at office hours. That letter can comment on your studious nature.

In summary, don't collect letters from all physicians (that is what you have to do for residency applications).  Get a diverse range of letters who can put a spotlight to the different aspects of your application and you as a person.