Many doctors, particularly young doctors, come to view test results as if handed down direct from the heavens -- and forget that context greatly alters their implications. It shouldn't be your burden to defend against this -- but alas, it is.
Verify you are getting the tests you need, and only the tests you need. Challenging such decisions is not an insult to your doctor. Simply, it is an affirmation of the fact that you, literally, have skin in the game.