Medicare's Open Enrollment Period runs October 15 through December 7 every year, and 2026 is no exception — this is the one guaranteed window when anyone with Medicare can change their coverage for the following year, no special circumstances required. * During those seven weeks, you can switch from Original Medicare to a Medicare Advantage plan, or drop a Medicare Advantage plan and go back to Original Medicare. You can also move from one Medicare Advantage plan to another, add or drop prescription drug coverage, or switch which Part D drug plan you're enrolled in. * Timing matters more than people expect: whatever change you make has to reach your plan by December 7, and the new coverage doesn't start until January 1 of the following year — there's no early activation, even if you make the switch the day the window opens. * This window is different from the Medicare Advantage Open Enrollment Period, which runs January 1 through March 31 and only lets people already in a Medicare Advantage plan make one additional switch. If you miss the October-December window entirely and aren't eligible for a special enrollment period, you'll typically have to wait until the following October to make changes. * Before switching anything, compare plans directly at medicare.gov's Plan Finder using your specific prescriptions and preferred doctors — the "best" plan varies enormously by individual medical needs, not just premium cost.