Every fall, tens of millions of Medicare beneficiaries get a narrow window to review their coverage and make changes for the following year. The Medicare AEP, or Annual Enrollment Period (also called the Annual Election Period), runs from October 15 through December 7, and decisions made during these 54 days determine your prescription and health-plan costs for the entire next calendar year. Missing this window or failing to review your plan’s changes can cost you hundreds or even thousands of dollars.
Important – verify current details: The Medicare AEP runs October 15 to December 7, and changes take effect January 1. This is different from the Medicare Advantage Open Enrollment Period (January 1 to March 31) and from Medigap enrollment, which follows its own rules. Dollar figures below, including the 2026 Part D deductible maximum ($615) and the annual out-of-pocket drug cap ($2,100), are estimates that change every year and vary by plan and location. This article is for general educational purposes only and is not insurance, financial, or medical advice. Always confirm current dates, benefits, and costs at Medicare.gov, by calling 1-800-MEDICARE, or with your State Health Insurance Assistance Program (SHIP) before making coverage decisions.
What Is the Medicare AEP?
The Medicare AEP is the annual enrollment period established under Medicare rules that allows beneficiaries to make changes to their Medicare Advantage (Part C) and Medicare Part D prescription drug coverage. It is not the same as the Initial Enrollment Period for people newly eligible for Medicare, and it is not the Medigap Open Enrollment Period. The AEP specifically governs annual plan switching for existing Medicare enrollees.
During the AEP, any changes you make take effect on January 1 of the following year. If you do not make any changes during the AEP, your current plan generally renews automatically for the next year with whatever new terms, premiums, and formulary changes your insurer has implemented. This passive renewal is exactly why reviewing your plan annually is so important – doing nothing is itself a decision.
What You Can Do During the AEP
The AEP gives you flexibility to restructure your Medicare coverage in several ways. You can switch from one Medicare Advantage plan to another; join a Medicare Advantage plan for the first time if you are currently on Original Medicare; drop your Medicare Advantage plan and return to Original Medicare; enroll in a standalone Medicare Part D plan; switch from one Part D plan to another; or drop your Part D plan entirely (though going without creditable drug coverage can trigger a late enrollment penalty later).
The one thing you generally cannot do during the AEP is enroll in or switch a Medigap (Medicare Supplement) plan on the basis of the AEP. Medigap enrollment is governed by separate rules, primarily your one-time six-month Medigap Open Enrollment Period that begins when you are 65 and enrolled in Part B, plus any guaranteed-issue rights you may have. For Medigap timing, see our Medicare enrollment guide.
AEP vs. Medicare Advantage Open Enrollment vs. Medigap
These three sets of rules are easy to confuse, so it helps to keep them separate. The AEP (October 15 to December 7) is the main annual window for changing Part D and Medicare Advantage coverage, effective January 1. The Medicare Advantage Open Enrollment Period, or MA OEP (January 1 to March 31), is a second, more limited window: if you are already enrolled in a Medicare Advantage plan, you may make one change – switch to a different MA plan or drop MA and return to Original Medicare (with the ability to add a Part D plan). The MA OEP does not apply to people on Original Medicare and does not allow standalone Part D-only switching for those not in an MA plan.
Medigap is different again. Medigap policies supplement Original Medicare and are sold by private insurers under federal and state rules. The best time to buy is during your one-time Medigap Open Enrollment Period, when insurers cannot deny you coverage or charge more for health reasons. Outside that window, buying or switching a Medigap policy may require medical underwriting in most states, though some states offer annual “birthday rule” or continuous guaranteed-issue protections. Because these rules vary by state, verify your situation before assuming you can change Medigap freely.
Why You Should Review Your Plan Every Year
Medicare Advantage and Part D plans can change their benefits, premiums, formularies, provider networks, and cost-sharing structures every year. Your plan is required to send you an Annual Notice of Change (ANOC) in the fall – generally by late September – detailing what will change on January 1. Common changes include premium increases, removal of drugs from the formulary or movement to higher-cost tiers, changes to copay and coinsurance amounts, narrowing or expanding of provider networks, and adjustments to extra benefits like dental, vision, or OTC allowances.
Even if you were satisfied with your plan this year, next year’s version may be significantly different. A drug that was on a lower tier at a modest copay might move to a higher tier at a much larger copay. Your primary care doctor might leave the network. The plan’s out-of-pocket maximum might rise. Reviewing the ANOC and comparing alternatives during the AEP is the only way to catch these changes before they take effect.
How to Prepare for the Medicare AEP
Start your preparation in September, well before the October 15 start date. Begin by reviewing the ANOC from your current plan. Make a list of all prescription drugs you take, including dosages, and all doctors and specialists you see. Then use the Medicare.gov Plan Finder to compare your current plan against alternatives in your ZIP code.
When comparing plans, focus on total estimated annual cost rather than just the monthly premium. The Plan Finder estimates your total drug costs based on the medications you enter. Also check whether your doctors are in each plan’s network and whether your drugs are covered on the formulary at a reasonable tier. A $0-premium plan that does not cover your medications well can end up costing far more than a plan with a modest premium.
If you are considering switching from Medicare Advantage to Original Medicare during the AEP, understand that you will typically need to add a standalone Part D plan and may want a Medigap supplement plan. However, Medigap enrollment outside your Medigap Open Enrollment Period may require medical underwriting in most states. This is an important consideration that our Medicare Advantage vs Supplement guide covers in depth.
Common AEP Mistakes to Avoid
The most common mistake is doing nothing. Many beneficiaries let their plans auto-renew without reviewing changes, only to discover higher costs or lost coverage mid-year. Another mistake is focusing only on premiums while ignoring drug formulary changes and network adequacy.
Some beneficiaries also confuse the AEP with the Medicare Advantage Open Enrollment Period. As noted above, the MA OEP (January 1 to March 31) allows one additional plan change only if you are already enrolled in a Medicare Advantage plan; it does not apply to standalone Part D plans or to people on Original Medicare.
Finally, do not wait until December 7 to make your decision. Selections made in the final days carry a higher risk of processing delays. Aim to complete your enrollment by early to mid-November so you have time to correct any errors.
AEP and Prescription Drug Coverage
Drug coverage is often the most important factor to evaluate during the Medicare AEP. For 2026, the standard Part D benefit includes a deductible of up to $615 (some plans have a lower or no deductible), an initial coverage phase where you typically pay 25 percent coinsurance on covered drugs, and then catastrophic coverage. Under the Inflation Reduction Act, annual out-of-pocket spending on covered Part D drugs is capped – for 2026 that cap is $2,100, up from $2,000 in 2025 (the cap is indexed and rises again in future years). Once you reach the cap, you pay nothing more for covered Part D drugs for the rest of the calendar year. These figures come from Medicare.gov and should be verified there, as they are updated annually.
If you take expensive brand-name or specialty drugs, the annual out-of-pocket cap is a significant protection. Many plans also offer the Medicare Prescription Payment Plan, which lets you spread your out-of-pocket drug costs across the year in monthly payments instead of paying large amounts at the pharmacy at once. Still, which drugs are covered and at what tier varies by plan, so use the Medicare.gov Plan Finder to enter every drug you take and compare estimated annual costs across available plans. For more on drug coverage costs, see our Part D donut hole article.
Frequently Asked Questions
What happens if I miss the AEP?
If you miss the October 15 to December 7 window, you are generally locked into your current plan until the next AEP, unless you qualify for a Special Enrollment Period due to a qualifying life event (such as moving or losing other coverage). Medicare Advantage enrollees can also make one change during the MA OEP from January 1 through March 31.
Can I change my Medigap plan during the AEP?
Not on an AEP basis. The AEP applies to Medicare Advantage and Part D plans. Medigap enrollment follows separate rules. You can apply to switch Medigap plans at other times, but outside your Medigap Open Enrollment Period, medical underwriting may apply in most states. Some states offer annual birthday-rule enrollment. See our compare Medicare supplement plans guide for details, and verify your state’s rules.
Is there a penalty for switching plans during the AEP?
No. There is no penalty for switching plans during the AEP. You can change Medicare Advantage plans or Part D plans as many times as you want during the 54-day window; only your final election before December 7 takes effect on January 1. (A separate late enrollment penalty can apply if you go without creditable drug coverage, which is different from switching between plans.)
How do I get help comparing plans?
Your State Health Insurance Assistance Program (SHIP) offers free, unbiased counseling from trained counselors. You can also use the Medicare.gov Plan Finder, call 1-800-MEDICARE, or work with a licensed insurance agent. Independent agents who represent multiple carriers can compare options side by side at no cost to you.
Can I switch from Original Medicare to Medicare Advantage during the AEP?
Yes. The AEP allows you to join a Medicare Advantage plan if you are currently on Original Medicare. Be aware that once you join Advantage, you should not keep paying for a Medigap policy (it is generally illegal for an insurer to sell you a new one while you are on Advantage). If you later want to return to Original Medicare with Medigap, underwriting may apply in most states.
Make the AEP Work for You
Treat the Annual Enrollment Period as your annual healthcare financial checkup. Read your ANOC, compare at least three alternative plans, and verify that your doctors and drugs are covered before making a decision. The 54-day window passes quickly, and the choices you make during this period lock in your costs and coverage for an entire year. For a comprehensive view of all enrollment windows and planning strategies, visit our healthcare policy guide and our guide to the last day for Medicare open enrollment.
Sources
- Medicare.gov, Your coverage options / when you can join, switch, or drop a plan – medicare.gov
- Medicare.gov, Costs for Medicare drug coverage (2026 Part D deductible and $2,100 out-of-pocket cap) – medicare.gov
- Centers for Medicare & Medicaid Services (CMS) – cms.gov
- State Health Insurance Assistance Programs (SHIP) – shiphelp.org