When can I enroll in Medicare?

Your Initial Enrollment Period

When you first become eligible at 65, you get a seven-month Initial Enrollment Period: the three months before your birthday month, your birthday month, and the three months after. This is when you sign up for Parts A and B and, if you want them, a Medicare Advantage or Part D plan. Signing up in the months before your birthday helps your coverage start without a gap.

The Annual Enrollment Period

Every year from October 15 to December 7, anyone with Medicare can make changes for the following year — join, drop, or switch a Medicare Advantage plan, and join, drop, or switch a Part D drug plan. Changes you make take effect January 1. This is the window most people use to shop their coverage as plans and prices change.

Other windows

If you're already in a Medicare Advantage plan, the Medicare Advantage Open Enrollment Period (January 1 to March 31) lets you switch to another Advantage plan or return to Original Medicare once. Separately, Special Enrollment Periods open when life changes — you move, you lose employer coverage, or you qualify for help — and let you enroll or switch outside the usual windows. If you missed your Initial Enrollment Period and don't qualify for a Special one, the General Enrollment Period (January 1 to March 31) is the fallback for Part B.