@gently True, MA HMOs require you to choose only doctors in your plan's network. But all plans must cover all medically necessary services that Original Medicare covers, as is stated plainly on Medicare.gov. My rheum ordered bone markers for me at my request even though they don't use them to guide clinical treatment so I got no useful info from my rheum re: the results in comparison to the bone markers I ordered and paid for myself prior to treatment on Forteo, and relied on information in this support group and elsewhere to interpret. My insurance did pay for the bone markers when my doctor ordered them. Whether my rheum indicated it was a medical necessity I can't say; I didn't ask them to and no longer have the order to refer to. But if it's true that neither OM or MA will pay for bone markers unless the ordering doctor says its a medical necessity, then in that respect there is no difference between OM and MA and no advantage to OM over MA. Yes, MA plans often require pre-approval for things whereas OM rarely does. That, like the network restrictions, is a difference in how OM and MA are administered. It is not a difference in coverage. If you want to say that having to get pre-approval in effect equals no coverage if it is delayed or denied, of course I respect your right to that opinion. But I'm curious, when OM denies claims, do you also regard that as not providing coverage? I've had both OM and MA, BTW. On OM I once had routine blood work denied that I had to fight to get them to pay for that was more time-consuming and frustrating than any PA. which has actually largely gone smoothly for me. In the end I am not trying to champion one over the other, however.