It's also the case that doctors have so many patients and so many ongoing medical advances and drugs to evaluate, that they often just diagnose and prescribe based on some general principles and 'average' situations. If you are not an 'average' medical case (as I am), complications can arise. My wife is very sensitive to medications, and she has to insist on smaller doses of some things to avoid bad reactions.
    We have several scary stories about close calls and bad experiences when some doctor or nurse didn't want hear about objections to some drug or procedure. It's a delicate matter to stand up to careless medical advice without upsetting the 'experts'.