You can still make some changes to your coverage after the annual enrollment period ends on December 7. However, there are restrictions on what you can do. During the Medicare Open Enrollment period ( January 1 – March 31 ), you can :  Switch to another Medicare Advantage Plan if you already have a Medicare Advantage Plan Leave your Medicare Advantage Plan and go back to Original Medicare During this period you can’t : Go from an Original Medicare to a Medicare Advantage Plan  Enroll in a Medicare Prescription Drug Plan (Part D) if you’re in Original Medicare Switch from one Part D plan to another if you have Original Medicare