Medicare Open Enrollment vs. Medicare Advantage Open Enrollment: What’s the Difference?
Medicare has two periods commonly called open enrollment, but they are not interchangeable—and using the wrong one could limit your choices.
The names may sound similar, but these two Medicare enrollment periods come with very different rules. Two enrollment periods contain the words “open enrollment,” but they apply to different people and allow different changes.
The fall Medicare Open Enrollment Period runs from October 15 through December 7. It gives Medicare beneficiaries broader opportunities to review and change Medicare Advantage and prescription drug coverage for the following year.
The Medicare Advantage Open Enrollment Period runs from January 1 through March 31. It is a more limited period available only to people who are already enrolled in a Medicare Advantage plan.
January through March is not a second full Annual Enrollment Period. It can provide a valuable opportunity to correct a Medicare Advantage choice, but it does not reopen every Medicare option.
Medicare Open Enrollment from October 15 through December 7 allows broader Medicare Advantage and Part D changes, while Medicare Advantage Open Enrollment from January 1 through March 31 is limited to people already enrolled in Medicare Advantage.
Medicare Open Enrollment vs. Medicare Advantage Open Enrollment at a Glance
| Enrollment rule | Medicare Open Enrollment | Medicare Advantage Open Enrollment |
|---|---|---|
| Dates | October 15–December 7 | January 1–March 31 |
| Who may use it? | People with Medicare who meet the eligibility rules for the coverage they want | Only people already enrolled in Medicare Advantage |
| Switch Medicare Advantage plans? | Yes | Yes—one permitted change |
| Original Medicare to Medicare Advantage? | Yes | No |
| Medicare Advantage to Original Medicare? | Yes | Yes |
| Change a standalone Part D plan? | Yes, when eligible | Not as a general standalone Part D change |
| Typical effective date | January 1 | First day of the month after the request is received |
Good to know: A qualifying event—such as moving, losing certain coverage, qualifying for Medicaid or receiving Extra Help—may create a Special Enrollment Period.
Why Are Both Periods Called “Open Enrollment”?
Medicare.gov calls the October 15 through December 7 period the Open Enrollment Period. Insurance professionals also frequently call it the Annual Enrollment Period, or AEP.
The January 1 through March 31 period is specifically called the Medicare Advantage Open Enrollment Period.
Advertisements and everyday conversations often shorten both names to “open enrollment.” That makes them sound interchangeable even though the rules are very different.
Same two words. Very different rulebook.
What Is Medicare Open Enrollment?
The annual Medicare Open Enrollment Period runs from October 15 through December 7. It is the main time to review Medicare Advantage and Part D prescription drug coverage for the coming year.
Changes made during this period generally become effective January 1, provided the enrollment request is received by December 7.
What you can do
- Switch from Original Medicare to Medicare Advantage.
- Switch from one Medicare Advantage plan to another.
- Leave Medicare Advantage and return to Original Medicare.
- Join, change or drop standalone Part D coverage when eligible.
What it does not do
- Enroll you in Part A or Part B for the first time.
- Create an automatic right to buy Medigap without underwriting.
- Replace your Initial Enrollment Period.
- Guarantee that every plan is available in your county.
Your current plan may still work—but it deserves a yearly review. Start with your Annual Notice of Change, then verify your prescriptions, providers, hospitals, pharmacies and expected costs.
What Is the Medicare Advantage Open Enrollment Period?
The Medicare Advantage Open Enrollment Period runs from January 1 through March 31 and is available only to people already enrolled in Medicare Advantage.
It provides one opportunity to switch Medicare Advantage plans or leave Medicare Advantage and return to Original Medicare.
What you can do
- Switch to another Medicare Advantage plan.
- Leave Medicare Advantage and return to Original Medicare.
- Join a standalone Part D plan when returning to Original Medicare.
What you cannot do
- Move from Original Medicare into Medicare Advantage through this period.
- Use it as a general standalone Part D shopping period.
- Make repeated Medicare Advantage changes during all three months.
- Treat it as a second full AEP.
A change generally begins on the first day of the month after the plan receives the enrollment request.
Keep using your current coverage until the new coverage is confirmed and effective.
Do not assume a requested change has already taken effect. Review your confirmation materials and keep your current plan information available until the effective date.
Why Medicare Advantage Open Enrollment Is Not a Second AEP
You must already have Medicare Advantage
Someone in Original Medicare cannot use this period simply because they changed their mind after December 7.
You receive one change
This is not a three-month period of unlimited Medicare Advantage plan switching.
Part D choices are limited
You may join standalone Part D when leaving Medicare Advantage, but it is not a general Part D change period.
Medigap has separate rules
Leaving Medicare Advantage is one decision. Qualifying for a Medicare Supplement policy is another.
Medicare Advantage Open Enrollment is a limited correction window—not a second full AEP.
Medicare Advantage Open Enrollment Is Not the General Enrollment Period
January 1 through March 31 is also the annual General Enrollment Period for certain people who need to enroll in Medicare Part B or premium Part A. That does not make the two periods the same.
| January–March period | What it is for |
|---|---|
| Medicare Advantage Open Enrollment | One permitted plan change for someone already enrolled in Medicare Advantage. |
| General Enrollment Period | Enrollment in Part B or premium Part A after missing an earlier opportunity, when eligible. |
How Are These Periods Different From Initial Enrollment?
Your Initial Enrollment Period is connected to when you first become eligible for Medicare. For many people becoming eligible at 65, it begins three months before the month they turn 65, includes their birthday month and ends three months afterward.
| Enrollment period | Primary purpose |
|---|---|
| Initial Enrollment Period | Start Medicare and choose initial coverage. |
| Medicare Open Enrollment | Review and change Medicare Advantage or Part D coverage for the coming year. |
| Medicare Advantage Open Enrollment | Make one limited change while already enrolled in Medicare Advantage. |
| General Enrollment Period | Enroll in Part B or premium Part A after missing an earlier opportunity, when eligible. |
| Special Enrollment Period | Make permitted changes following certain qualifying circumstances. |
For a complete explanation of Initial Enrollment, General Enrollment, Special Enrollment and other important Medicare dates, read Medicare Enrollment Periods: Chart, Dates and Rules Explained.
Returning to Original Medicare Does Not Automatically Guarantee Medigap
Returning to Original Medicare does not automatically create a new federal Medigap Open Enrollment Period.
Your federal Medigap Open Enrollment Period is generally a one-time six-month period that starts the first month you have Medicare Part B and are 65 or older.
Outside that window, an insurer may be allowed to use medical underwriting unless you have a guaranteed-issue right or another protection under federal or state law.
Confirm whether you can obtain the Medigap coverage you want.
Review Medigap eligibility, underwriting, prescription drug coverage and effective dates before finalizing the change.
Which Medicare Enrollment Period Applies?
Your Medicare Advantage network is changing next year
Likely period: Medicare Open Enrollment, October 15 through December 7.
Your new Medicare Advantage plan is not working in January
Likely period: Medicare Advantage Open Enrollment, because you are already enrolled in Medicare Advantage.
You have Original Medicare and want Medicare Advantage in February
Likely period: MA OEP generally does not apply. Another enrollment opportunity would be needed.
You want to change standalone Part D plans in March
Likely period: MA OEP generally does not apply to this standalone Part D change.
You want Original Medicare and Medigap
Likely period: You may leave Medicare Advantage during AEP or MA OEP, but Medigap eligibility must be evaluated separately.
Common Medicare Open Enrollment Mistakes
Assuming January through March is a complete do-over
It provides one limited Medicare Advantage change, not every option available in the fall.
Waiting until January to change standalone Part D
A person in Original Medicare generally cannot use MA OEP simply to switch standalone drug plans.
Dropping Medicare Advantage before checking Medigap eligibility
Returning to Original Medicare does not automatically guarantee a Medicare Supplement policy.
Looking only at the premium
Review providers, prescriptions, pharmacies, prior authorization and maximum out-of-pocket exposure.
Assuming covered means the cost stayed the same
Coverage may remain while the tier, copayment, coinsurance or prior-authorization requirement changes.
What Should You Review During Medicare Open Enrollment?
Your medical care
- Doctors and specialists
- Hospitals and health systems
- Expected procedures and treatments
Your prescriptions
- Medication names and dosages
- Formulary tiers
- Prior authorization
- Preferred pharmacies
Your costs
- Premiums and deductibles
- Copayments and coinsurance
- Maximum out-of-pocket limit
Your lifestyle
- Travel and time in another state
- Dental, vision and hearing benefits
- Whether your priorities changed
Review Your Medicare Coverage Before December 7
Your current Medicare plan may still work—but it deserves a yearly review. The Free Medicare Open Enrollment Checklist walks you through what to check before deciding whether to keep or change your coverage.
Medicare Open Enrollment Questions
What is the difference between Medicare Open Enrollment and Medicare Advantage Open Enrollment?
Fall Open Enrollment allows broader Medicare Advantage and Part D changes. Medicare Advantage Open Enrollment is limited to current Medicare Advantage members and allows one plan change or a return to Original Medicare.
When is Medicare Open Enrollment for 2027 coverage?
October 15 through December 7, 2026, for changes generally effective January 1, 2027.
Can I join Medicare Advantage between January 1 and March 31?
Not through MA OEP if you currently have Original Medicare. Another enrollment opportunity would be needed.
How many times can I change Medicare Advantage plans between January and March?
One permitted Medicare Advantage change during the annual MA OEP.
Can I automatically get Medigap after leaving Medicare Advantage?
No. Medigap has separate enrollment, underwriting and guaranteed-issue rules.
Want Help Reviewing Your Medicare Options?
Medicare rules are national, but plan availability, provider networks, prescriptions and personal needs are not. From the first conversation through enrollment, you work directly with me.
No call centers. No 1-800 numbers. Just Robin.
Keep Reading
Robin Dall
Medicare Broker & Educator
Licensed Since 2013 • NPN 17032552
Robin Dall is an independent Medicare and Life Insurance agent who helps people turning 65 and current Medicare beneficiaries understand enrollment periods, Medicare Advantage, Original Medicare, Medigap and Part D coverage. She is based in Parrish, Florida and is licensed in Florida, Kansas, Missouri, Ohio, Texas, Arizona and North Carolina. From the first conversation through enrollment, clients work directly with Robin—not a call center.
That’s Medicare, minus the headache.
