With Medicare Advantage, prior authorization is needed for some treatments or services. This is generally not the case for traditional Medicare., This need for prior authorization can make Part C participants more susceptible to denials of coverage — even after paying for a service and awaiting reimbursement., Part C plans have networks you must use in order to pay the lowest costs for your healthcare. In some instances, local hospitals and your current healthcare team members may not be included in your plan’s network., Part C plan networks are also local, so national coverage will be out-of-network, and more expensive.