Why would a doctor even know how much a lab test costs? I wouldn’t expect my doctor to know that, on top of everything else he has to know. If I wanted to know, I’d either call the lab myself and ask, or I’d ask my doctor’s assistant to do that for me.
Like many men, I wait until my wife tells me. 
“I’m one stomach flu away from my ideal weight!”
For some patients it’s critical information. In some cases there might be a much cheaper diagnostic that may not be the latest thing but that the patient can afford.
My point wasn’t that patients don’t need to know how much tests costs, it was that doctors don’t necessarily have that information. And you could call the lab, or ask the doctor’s assistant to find out the cost for you. I would not expect the doctor to know how much a lab charges for a particular test.
Indeed. My father spent years overweight and being nagged by our family doctor, who was pretty strict on these things. Dad once complained to me that if you went in with a problem with your ear, that doctor would say it was because you’re overweight. Even though he changed doctors, this history, combined with a generational fear of making a fuss and a general disinclination towards medical intervention left him very reluctant to go to the doctors, especially for anything possibly related to being overweight (like say fatigue).
So he was thrilled about a year ago when he managed to lose 2 stones over the course of a few months. He told me he and his wife had been eating more carefully and trying to do more exercise. In retrospect alarm bells should have been ringing since his wife hadn’t lost anything like as much and the lifestyle changes seemed quite moderate. I was a bit worried about diabetes, but he said his blood sugar had been checked about a year before and was fine.
He’s just been diagnosied with a rare and not very treatable form of lymphoma, which is at stage IV. His haemoglobin was about half what it should be, but he hadn’t wanted to go to the doctors with fatigue, as he thought they’d say he needed to lose weight. Lesson: if your previously unsuccessful diet suddenly starts paying off a lot better without you having to try harder, the weight loss may not be unintentional or even unexpected, but it still might be worth getting checked out.
If one has insurance a routine exam, even with bloodwork etc is 0-$25. If you don’t have insurance, just tell your MD, and have him do tests as appropriate.
What is a nurse-practioner?
My experience is that without insurance it’s almost impossible to even get some tests. When I was uninsured I ran into facilities where their billing equipment was set up so that you HAD TO enter insurance information, and if you didn’t have any, too bad.
Very roughly, a nurse with advanced training allowing her to take on role somewhat between that of a traditional nurse and a doctor. Here’s the wiki on the profession.
Unlike traditional nurses, they can diagnose and prescribe treatment although not to the full extent than a doctor does. For routine things like child ear infections, minor illness and injury, and so forth they’re pretty much the same as doctors. For more difficult cases they’re supposed to refer to an actual doctor.