When would I need to get a third opinion?

If you get a differing second opinion and the two doctors (your first doctor and the second-opinion doctor) disagree on which is more valid, it may be necessary to get a third opinion. Many insurance plans will pay for it.

You won't just be going with the best two of three, by the way. In adding a third diagnosis, there are ways of digesting all of the information to make the most informed decision possible; it's highly likely that your first two physicians both made correct observations, even though they disagreed, and this may mean you need to take a completely new path than what you had been contemplating.

And this is call to bone up on the research: Just like smart detectives working a case, smart patients have saved their own lives (and the lives of relatives and friends) by doing their own research legwork, especially in cases when there's disagreement among doctors. Knowing where to find good health research is never more valuable than in a situation that calls for a second (or third) opinion.