Medicare's Annual Enrollment Period runs October 15 to December 7 every year. In those weeks you can join, switch, or leave a Medicare Advantage plan and change your Part D drug plan, with changes taking effect January 1. Medigap follows separate rules, so this window does not guarantee a Medigap switch.
What you can change between October 15 and December 7
- Join a Medicare Advantage plan if you have Original Medicare.
- Switch from one Medicare Advantage plan to another, including from an HMO to a PPO.
- Leave Medicare Advantage and return to Original Medicare. You will generally need a standalone Part D plan for prescription drugs.
- Join, switch, or drop a Part D prescription drug plan.
Anything you choose by December 7 takes effect January 1.
What this window does not change: Medigap
A Medigap policy is not part of Annual Enrollment. Outside your Medigap open enrollment period, which is six months starting the month you are 65 or older and enrolled in Part B, an insurer can ask health questions before it sells you a policy.
California adds one exception. If you already have a Medigap policy, the state's birthday rule gives you 60 days after your birthday to move to a policy with the same or lesser benefits without health questions. We explain it in the Plan G vs Plan N guide.
January 1 to March 31: the Medicare Advantage Open Enrollment Period
If you are already in a Medicare Advantage plan, you get one more change after the new year. You can switch to a different Medicare Advantage plan or go back to Original Medicare and add a Part D plan.
You cannot use it to join Medicare Advantage from Original Medicare. If you are on Original Medicare and miss December 7, you generally wait for the next fall window unless you qualify for a special enrollment period.
Read your plan's notice before you decide anything
Medicare Advantage and Part D plans send an Annual Notice of Change by the end of September. It lists what is different next year. Check four things in it:
- Is each of your doctors and your hospital still in the network?
- Is each of your prescriptions still on the drug list, and at the same cost tier?
- Did the premium, the copays, or the out-of-pocket limit change?
- Did any extra benefit you use, such as dental or vision, change?
A plan that worked for 2026 can quietly drop a doctor or raise a copay for 2027. If you do nothing, you stay in your current plan, so the review is what protects you.
Other times you may be able to change plans
Special enrollment periods exist for events such as moving out of your plan's service area or losing other coverage. If you are turning 65, your initial enrollment window is seven months: the three months before your birthday month, the birthday month, and the three months after.
Frequently asked questions
When does Medicare Annual Enrollment end?
It ends December 7. Choices made during the window take effect January 1.
Do I have to do anything if I like my plan?
No. You stay in your current plan if you do nothing. Plans change networks, drug lists, and costs every year, so read the Annual Notice of Change before you let it renew.
Can I change my Medigap policy during Annual Enrollment?
Annual Enrollment does not cover Medigap. Outside your Medigap open enrollment, an insurer can ask health questions, except in situations such as California's 60-day birthday rule.
Can I join Medicare Advantage in January?
Not from Original Medicare. The January 1 to March 31 period is for people already in a Medicare Advantage plan who want to switch plans or return to Original Medicare.