This is a tough one. Most doctors are independent contractors, not hospital employees. So while you may go to an in-network hospital, it's not uncommon for an out-of-network doctor to treat you. Unless you ask, you have no way of knowing up front. In emergency situations, asking your doctor what insurance he accepts is likely the last thing on your mind. But if you or someone you are with has the presence of mind to ask, your savings account may thank you for it later.