Hey sbx,
I'm not an ftm nor do I know anything about top surgery, but I can share my labwork experiences with you. I've had to pay out of pocket for bills that were quite insane (one was almost $3,000 and the other was around $700) but that's mainly because of the cost of estradiol/testosterone testing and choosing a hospital branch for one. Mainly the high cost is a result of some labs sending their speciality testing (like estradiol and testorone) to other labs (I know this because it's happened to me and have seen this happen with others). For general labwork, like a Complete Metabolic Panel, you probably won't pay too much. Actually, my $700 bill has a CMP down for $53 alone, so it's not bad. As long as they are just testing basic things for general medical clearance and not doing speciality testing the costs probably won't be a lot, likely well under 500 depending on the lab you go to. You can check this by looking at the blood work script itself and finding out the cost of each specific test, just in case.
Have you used the medicare policy for bloodwork before? How about for bloodwork for your endocrinoligist, if you have one. It may give you a better sense of your policy and whether you will need to code it a certain way.
By the way, take what I say with a grain of salt. This is only my experience, but it's been backed up by what I've seen through working in a medical office. In any case, I hope it helped somewhat.
