Yes, you can disenroll from a Medicare Advantage plan and return to Original Medicare. You can make this transition during the annual Medicare Open Enrollment Period (October 15 to December 7) for coverage starting January 1, or during the Medicare Advantage Open Enrollment Period (January 1 to March 31). Be aware that if you wish to purchase a Medigap supplemental policy upon returning to Original Medicare, you may be subject to medical underwriting depending on your state and how long you have been enrolled in Advantage.