I recently had a home sleep study test- my doctor said my overnight oximeter results weren't great and would like me to have a formal sleep study. Is this test covered, if so is it covered in full or would I have a balance to pay?

I recently had a home sleep study-my doctor said my overnight (from this test) oximeter results weren't great and would like me to have a formal sleep study.  Is this test covered, if so is it covered in full or would I be responsible for a remaining balance.