Letters of Recomendation

Hello, 

I am asking people to write letters of recommendations but don't know if I am asking the right people. I heard schools require 2 letters from PA's or Physicians. I have a letter of recommendation from my advisor who I also had as a professor and TAd for but I made very good relationships with an NP I think who I think would write the best letter but I don't know if it will be a problem