What Medicare AEP Is and When It Happens

Medicare Annual Enrollment Period (AEP) is the one time each year when you can change your Medicare coverage without penalty. During AEP, you can switch between Original Medicare and Medicare Advantage plans, change your prescription drug plan, or drop coverage altogether. The window runs from October 15 to December 7 each year, and any changes you make take effect on January 1 of the following year.

Outside of AEP, you cannot switch plans unless you have a may have access to life event — such as losing employer coverage, moving to a new state, or becoming newly may be able to access for Medicare. If you try to change plans outside AEP without a may have access to event, your request will be denied. This is why the three-month window matters: it is your may provide chance each year to reassess your coverage and move to a plan that better fits your health needs or budget.

AEP is different from the Initial Enrollment Period (IEP), which is the seven-month window around your 65th birthday when you first become may be able to access for Medicare. It is also different from the Medicare Advantage Open Enrollment Period (January 1 to March 31), which allows Medicare Advantage members only to switch to a different Advantage plan or return to Original Medicare.

Key Takeaways

  • Medicare AEP runs October 15 to December 7 each year, and changes take effect January 1.
  • During AEP you can switch from Original Medicare to Medicare Advantage, change prescription drug plans, or drop coverage — but you cannot make these changes at any other time without a may have access to life event.
  • You do not have to do anything during AEP if you are happy with your current plan; inaction means your coverage continues as is.
  • Your plan's costs, covered drugs, and network doctors change each year, so reviewing your options annually can save you money or prevent coverage gaps.

Why You Should Review Your Coverage During AEP

Even if you have been on the same plan for years, the plan itself changes every January. Your monthly premium may go up or down. The drugs your plan covers may shift — a medication you take might move to a higher cost tier, or a new generic might become available at a lower price. Your doctor or pharmacy might leave the network. Reviewing your plan each October takes a few hours and can prevent surprises later.

The most common mistake is assuming your plan works the same way it did last year. Medicare Advantage networks shrink and expand. Original Medicare with a Medigap policy stays stable, but Medigap premiums rise annually. Prescription drug plans shuffle their formularies — the list of covered medications — every year. If you take multiple medications, the plan that was cheapest last year might cost significantly more this year.

You can review plan changes without committing to anything. Medicare.gov lets you compare plans side by side, showing premiums, deductibles, copays, and which drugs are covered. Many people find that spending an hour on this comparison during October saves them hundreds of dollars in the year ahead.

How to Compare Plans During AEP

Start at Medicare.gov, the official Medicare website. Log in with your Medicare account or create one using your Social Security number and date of birth. Go to the "Find Care Providers and Suppliers" or "Compare Plans" section. You will need your current prescriptions list — get this from your pharmacy or doctor's office before you start.

Enter your zip code, your medications, and your preferred doctors and pharmacies. Medicare will show you all available plans in your area, ranked by estimated cost. The tool estimates what you will pay in premiums, deductibles, copays, and coinsurance for the year ahead, based on your prescriptions and the doctors you use. Pay attention to the total estimated cost, not just the monthly premium.

If you use a pharmacy that is not in a plan's network, or if a drug you take is not covered, the plan will flag this. Some people find that switching to a different pharmacy or a generic version of their medication opens up cheaper plan options. If you need help comparing, you can call 1-800-MEDICARE and speak with a counselor, or contact your State Health Insurance information Program (SHIP) — a free counseling service in every state.

Making Changes During AEP

Once you have decided to switch plans, you have three ways to enroll: online at Medicare.gov, by phone at 1-800-MEDICARE, or through your plan directly. Online enrollment is fastest — you can complete it in 15 to 20 minutes. By phone, a representative will walk you through the process and answer questions as you go. Some plans also have their own enrollment websites or phone numbers.

When you enroll, you will choose an effective date. Most people choose January 1, which is the standard start date for all plan changes made during AEP. If you enroll after December 7, your change will not take effect until the following January 1 — there is no rush to enroll on the first day of AEP.

After you enroll, you will receive a confirmation letter from your new plan within two weeks. Review it carefully to make sure your doctors and pharmacies are listed correctly and your medications are covered. If something is wrong, contact the plan when ready — you have until December 31 to make corrections before your coverage starts.

What Happens If You Miss the AEP important date

If October 15 to December 7 passes and you have not made a change, your current plan renews automatically for the next year. You do not lose coverage. However, you will be locked into that plan for the next 12 months unless you experience a may have access to life event.

may have access to events include losing employer coverage, moving to a new state, getting married or divorced, having a baby, or becoming newly may be able to access for Medicare. If any of these happen, you have 60 days to make a plan change. You will need to report the event to Medicare and provide proof — such as a termination letter from your employer or a marriage certificate.

If you miss AEP and do not have a may have access to event, you will have to wait until the following October 15 to change plans. This is why setting a calendar reminder in early October is worth doing — missing the window by a few days can cost you a full year of higher premiums or worse coverage.

Special Situations: Employer Coverage and Medicaid

If you are still working and covered by your employer's health plan, you may not need to enroll in Medicare Part B or Part D right away. However, you should still review your Medicare options during AEP, because your employer coverage may end when you retire. Some people enroll in Original Medicare and a Medigap plan during AEP even though they are not using it yet, to lock in better rates before they retire.

If you have both Medicare and Medicaid (dual may be able to access), your state Medicaid program may restrict which Medicare Advantage plans you can join. Some states require dual-may be able to access people to enroll in specific plans. Check with your state Medicaid office or your SHIP counselor before the AEP important date to understand your options.

If you lose Medicaid during the year, you have 60 days to enroll in a Medicare plan outside of AEP. This is a may have access to event, so do not wait until October if your Medicaid ends in June.

Common Mistakes to Avoid During AEP

The biggest mistake is waiting until December 6 to enroll. While you can enroll right up to the important date, plans sometimes experience high volume in the final days, and confirmation letters may arrive after January 1. Enroll by mid-November to give yourself time to fix any errors.

Another mistake is choosing a plan based only on the monthly premium. A plan with a $0 premium might have a $500 deductible and high copays. A plan with a $50 premium might have no deductible and $5 copays. The total cost — premium plus out-of-pocket costs — is what matters. Medicare.gov's comparison tool estimates this for you.

Do not assume your doctor is in a plan's network just because they were last year. Networks change. Call your doctor's office or the plan directly to confirm they are in-network for 2025. If your main doctor is not in a plan, that plan is probably not the right choice for you, even if it is cheaper.

Frequently Asked Questions

Can I change plans more than once during AEP?

Yes. You can enroll in a new plan, then change your mind and enroll in a different one — as long as you do it before December 7. Only your final enrollment counts. However, do not use this as a strategy; each enrollment takes time to process, and mistakes happen. Make your decision once and stick with it.

What if my plan is being discontinued?

If your current plan is ending, Medicare will send you a notice by September 30. You must choose a new plan during AEP. Medicare will not automatically move you to another plan. If you do not choose, you will lose coverage on December 31. Check your mail in September for this notice.

Do I have to enroll in Part D if I do not take any medications?

You are not required to enroll in Part D if you do not take prescription drugs. However, if you enroll later when you do need medications, you may face a late enrollment penalty — a permanent increase to your Part D premium. If there is any chance you will need prescriptions in the future, enrolling now is usually cheaper than paying the penalty later.

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

Yes. You can switch from Original Medicare to a Medicare Advantage plan, or from Medicare Advantage back to Original Medicare, during AEP. If you switch to Original Medicare, you should also enroll in a Medigap plan and Part D during the same window, because your enrollment rights are limited after AEP.

What if I enroll in a plan by mistake?

You have until December 31 to cancel an enrollment and choose a different plan. Contact your new plan or call 1-800-MEDICARE to cancel. Your previous plan will not automatically restart — you must actively enroll in a different plan before the important date.