Employers power to prevent surgery?

I am currently waiting for a surgery date for weight loss surgery.
For months now I have been told by my employer that I had to wait until mid
September to schedule my surgery because my fellow employees would be
on vacation. Lucky for them I'm having issues with getting my iron level up to par. Now that I am pursuing ways to raise my iron level I kind of expect to have a surgery date by late October maybe November. So I tell my boss this
and now they're telling me that I have to wait until 2 of my
co-workers return from surgery. One is going to be out at least 6
weeks starting 10/18 and the other doesn't have a date set yet and
there's no telling how long she'll be out. I'm so frustrated! My
clearance is only good for six months so I have to have it by February
but it's not fair that I should have to wait. One employee is having a
hysterectomy and has precedence over me because this is medically
necessary (mine is not?) and the other is a comp case so naturally her
situation is more important than mine. If it weren't for the health
insurance I would be looking for another job now. My question is what repercussions could I face if I took the surgery date offered against my employers wishes? What power do they have to stop what is medically necessary in both my opinion and that of my doctor?

Thank you,
Carrie

Not if the doctor says it is medically needed...they cannot stop that and cannot punish you for that.