Medicare Annual Enrollment Period: What Can You Change?

The Medicare Annual Enrollment Period runs from October 15 to December 7 every year, and it’s the one window when all Medicare beneficiaries can make changes to their coverage for the coming year. If you’re on Medicare and your plan is raising its premiums, dropping drugs from its formulary, or narrowing its network, this is your window to act. Sit on your hands and you’re locked in for another full year.

Here’s exactly what you can change during the AEP, what you can’t, and how to use the time wisely.

What Is the Medicare Annual Enrollment Period?

The Medicare Annual Enrollment Period, also called the AEP or Medicare Open Enrollment, is a federally mandated 54-day window that runs October 15 through December 7 each year. Any changes you make take effect January 1 of the following year. According to CMS, this is the primary opportunity for Medicare beneficiaries to review and adjust their Part C and Part D coverage.

The AEP is different from your Initial Enrollment Period, which is the seven-month window when you first become eligible for Medicare at 65. It’s also separate from the Medicare Advantage Open Enrollment Period, which runs January 1 through March 31 and allows a more limited set of changes for people already enrolled in a Medicare Advantage plan.

The AEP is the broadest window for making changes. During this period, you have the full range of options available, regardless of what kind of Medicare coverage you currently have. It’s the annual reset that gives everyone on Medicare a chance to reconsider their plan.

What Changes Can You Make During Medicare Open Enrollment?

During the AEP, you can make any of the following changes, and they all take effect January 1:

• Switch from Original Medicare to a Medicare Advantage plan, or switch from Medicare Advantage back to Original Medicare with or without a standalone Part D drug plan.
• Switch from one Medicare Advantage plan to another Medicare Advantage plan, including plans with different premiums, networks, or drug coverage.
• Join, drop, or switch standalone Medicare Part D prescription drug plans if you are on Original Medicare.

These are meaningful options. If your Medicare Advantage plan is raising its out-of-pocket maximum, adding prior authorization requirements, or dropping your specialist from its network, the AEP is your chance to move. If you’ve been on Original Medicare and are now interested in an Advantage plan that covers dental and vision, this is when you make that switch.

Jonathan Potter reviews Medicare plans with clients during the AEP each year, and one of the most common findings is that people auto-renew without realizing their plan has changed significantly. A plan that was a good fit in 2024 may have adjusted its formulary, raised its copays, or narrowed its provider network for 2025. The changes are disclosed in the Annual Notice of Change letter your plan sends each September, and reviewing it is worth your time before October 15.

What Cannot Change During the Medicare Annual Enrollment Period?

The AEP does not let you add or change a Medicare Supplement, or Medigap, plan. Medigap operates on different enrollment rules. If you want to add a Medigap policy to complement Original Medicare, you can do so at any time, but outside your six-month Medigap Open Enrollment Period at age 65, insurers in most states can use medical underwriting to charge more or deny coverage based on your health history.

The AEP also does not apply to Medicare Parts A and B themselves. If you need to enroll in Part A or Part B for the first time and you’ve missed your Initial Enrollment Period, the General Enrollment Period from January 1 through March 31 is where that happens, with coverage starting July 1 and a potential late enrollment penalty.

Cost-sharing reductions, Medicaid, and dual-eligible special needs plans have their own enrollment rules and are not governed by the AEP. If you have a low income and may qualify for Extra Help with Part D costs or a dual-eligible plan, those programs have year-round enrollment.

How Should You Use the Medicare Annual Enrollment Period?

The most effective way to use the AEP is to treat it as an annual review rather than a formality. Pull out the Annual Notice of Change your plan sent in September and read through the changes to premiums, cost-sharing, formulary, and network for the coming year. Then use the Medicare Plan Finder at medicare.gov to run a comparison of available plans in your area based on your specific medications and preferred providers.

If you take multiple prescriptions, run each one through every plan you’re considering. A medication that costs $10 per fill on one plan may cost $60 on another, and the difference over 12 fills adds up to $600 annually before you’ve considered other cost-sharing differences.

Reviewing your Medicare coverage options with a broker during the AEP costs you nothing and typically takes less than an hour. A broker can do the plan comparison work for you, check your doctors’ network status across multiple plans, and run your prescriptions through each plan’s formulary. Most people who do this annual review find at least one reason to consider a change, even if they ultimately decide to stay with their current plan.

What Happens If You Miss the Medicare Annual Enrollment Period?

If you miss the December 7 deadline, your current coverage automatically renews for the next year, with any changes your plan has made to its benefits, premiums, and network. You are locked into that coverage until the next AEP, unless you qualify for a Special Enrollment Period due to a qualifying event.

There is one additional option if you’re on Medicare Advantage. The Medicare Advantage Open Enrollment Period from January 1 through March 31 allows people already enrolled in a Medicare Advantage plan to switch to a different Advantage plan or return to Original Medicare with a Part D plan. The MAOEP is more limited than the AEP, but it does give people who regret a December decision a second chance. Changes made during the MAOEP take effect the first day of the following month.

Reach out to Beacon Insurance Advisors before October 15 to have your plan reviewed before the AEP opens so you’re ready to make a well-informed decision, not a rushed one, before the December 7 deadline.

FREQUENTLY ASKED QUESTIONS

Can I switch from Medicare Advantage to Original Medicare during the AEP?

Yes. Switching from Medicare Advantage to Original Medicare is one of the primary purposes of the AEP. If you make that switch, your Original Medicare coverage begins January 1. You should also enroll in a Part D drug plan during the AEP if you want drug coverage under Original Medicare. Be aware that adding a Medigap supplement after returning to Original Medicare may involve medical underwriting in most states, so your health history could affect your eligibility or premium.

Does the Annual Enrollment Period apply to Medigap policies?

No. Medigap has separate enrollment rules. You can apply for a Medigap policy at any time of year, but guaranteed issue rights that prevent insurers from denying coverage or charging more based on health history are only available during specific windows, most importantly your six-month Medigap Open Enrollment Period when you first enroll in Medicare Part B. Outside those windows, most states allow medical underwriting for new Medigap applicants.

How do I compare Medicare plans during the Annual Enrollment Period?

The Medicare Plan Finder at medicare.gov lets you enter your medications and see drug costs across available Part D and Medicare Advantage plans in your area. An independent broker can do this comparison on your behalf, check your doctors’ network status, and walk you through the full-year cost differences between plans, not just the monthly premium. Both resources are free to use.

The Medicare Annual Enrollment Period is your yearly opportunity to make sure your coverage still fits your health and your budget. Plans change every year, and the plan that was right in 2024 may not be right for 2025. Review your Medicare plan options before the December 7 deadline so you’re not locked into coverage that no longer serves you.