Updated November 2026 · Reviewed by the CoverageCo team
Medicare Advantage Open Enrollment runs January 1 through March 31 and lets people already enrolled in an Advantage plan make one change, switch to a different Advantage plan, or return to Original Medicare and add a Part D plan. It's not available to people on Original Medicare.
Key takeaways
- January 1 – March 31, and only if you're already in an Advantage plan.
- One change only, and it takes effect the first of the following month.
- It does NOT give guaranteed-issue rights to buy Medigap.
- Useful when a plan turns out to work differently than expected in January.
Who it's for, and who it isn't
This window exists for people who enrolled in a Medicare Advantage plan and then discovered, in the first weeks of the year, that it doesn't fit, a doctor left the network, a drug landed on a worse tier, referrals turned out to be a problem.
If you're on Original Medicare, this window doesn't apply to you. It's specifically a correction mechanism for Advantage enrollees.
| You can | You cannot |
|---|---|
| Switch to a different Advantage plan | Join an Advantage plan from Original Medicare |
| Return to Original Medicare | Make more than one change |
| Add a Part D plan when returning to Original Medicare | Switch from one standalone Part D plan to another |
The Medigap catch, again
Returning to Original Medicare during this window does not automatically give you the right to buy a Medigap policy.
Unless you're inside your one-time Medigap open enrollment period or qualify for a specific guaranteed-issue right, such as a trial right if you joined Advantage when first eligible, insurers in most states can still medically underwrite you and decline coverage.
So you can leave an Advantage plan in February and find yourself on Original Medicare with no supplement and no ability to buy one. Confirm your Medigap options before you make the change, not after.
How to use it well
If something about your plan is wrong, act early in the window rather than late. Changes take effect the first of the following month, so a February decision means March coverage.
Bring the specifics: which doctor is out of network, which drug moved tiers, what the actual cost difference is. That's what lets an agent find something that genuinely fixes the problem rather than trading one mismatch for another.
And if your current plan is still the best available option, that's a legitimate outcome worth knowing rather than guessing at.
Common questions
When is Medicare Advantage Open Enrollment?
January 1 through March 31 each year. It's only available to people already enrolled in a Medicare Advantage plan, and allows one change. Confirm current dates at Medicare.gov.
Is Medicare Advantage Open Enrollment the same as AEP?
No. AEP runs October 15 to December 7 and is open to everyone on Medicare. This January window is only for people already in an Advantage plan and permits a single change.
Can I buy a Medigap policy during this window?
Not with guaranteed acceptance. Returning to Original Medicare doesn't automatically create Medigap rights, outside your one-time window or a specific guaranteed-issue situation, most states allow medical underwriting.
When does my new plan start?
Changes generally take effect the first day of the month after you make them, so acting early in the window means less time on a plan that isn't working.