Every fall, a notice from your Medicare plan shows up describing what is changing next year, and the ads start soon after. The Medicare Annual Enrollment Period is the window when you can act on it: it runs from October 15 to December 7, and whatever you choose takes effect on January 1. The window is generous about some changes and silent about others, and the one it is silent about (Medigap) is where people most often get caught. Here is what you can change, what you cannot, and what to check before you decide.
What is the Medicare Annual Enrollment Period?
The Annual Enrollment Period (AEP), which Medicare also calls Open Enrollment, is set by federal law as October 15 through December 7 of the year before your coverage year. So choices made between October 15 and December 7, 2026 are for 2027 coverage, starting January 1, 2027.
You can make more than one change during the window. If you do, the last plan choice you make before December 7 is generally the one that counts. And if you do nothing, you usually stay in your current plan for next year, with whatever changes the plan has announced.
AEP is for people who already have Medicare. If you are signing up for Part A and Part B for the first time, your own Initial Enrollment Period around your 65th birthday or another enrollment period governs that, not AEP.
What you can change during AEP
During the Annual Enrollment Period you can:
- Switch from Original Medicare to a Medicare Advantage (Part C) plan.
- Leave a Medicare Advantage plan and return to Original Medicare.
- Move from one Medicare Advantage plan to another, including between plans with and without drug coverage.
- Join a Part D prescription drug plan, switch to a different one, or drop drug coverage.
What AEP does not change: Medigap
AEP is a Medicare enrollment window. It is not a Medigap enrollment window, and that is where many people are caught off guard. A Medigap (Medicare Supplement) policy is private insurance that works with Original Medicare, and federal law does not give you a guaranteed right to buy one during AEP. Outside your protected windows, a Medigap insurer can generally ask health questions and decline you or charge more.
This matters most if you are thinking about leaving a Medicare Advantage plan for Original Medicare. You can make that switch during AEP, but getting a supplement to go with it is a separate question. Some people have a guaranteed right, for example if they joined Medicare Advantage for the first time within the past year under what Medicare calls a trial right, and a few states have their own Medigap rules. Check whether you would qualify for a supplement before you give up your Advantage plan, not after.
Dropping drug coverage deserves the same care. If you go without creditable drug coverage for a stretch and enroll in Part D later, you may owe a late enrollment penalty for as long as you have Part D.
Read your Annual Notice of Change first
If you are in a Medicare Advantage or Part D plan, your plan sends an Annual Notice of Change (ANOC) before AEP opens, usually by the end of September. It lists what your plan is changing for next year. Plans can change premiums, deductibles, copays, provider networks and the list of covered drugs from one year to the next, so last year's good fit is not automatically this year's.
When you read it, look for:
- Your drugs: whether each one is still covered, which tier it sits on, and whether it now needs prior authorization or step therapy.
- Your doctors, hospitals and pharmacies: whether they are still in network. Our guide to in-network vs. out-of-network care explains why that changes what you pay.
- Your costs: the premium, deductible, copays and the plan's yearly out-of-pocket limit, not just the premium on its own.
- Extra benefits such as dental, vision or hearing, if you rely on them.
How to decide before December 7
Start with a written list of every prescription with its dose, and every doctor and pharmacy you want to keep. Then compare plans against that list rather than against the ads. A plan with a low premium can cost more over a year if your drugs sit on a high tier or your specialist is out of network.
If you are weighing the bigger switch between the two paths, our comparison of Medicare Advantage and Original Medicare walks through the trade-offs in network access, drug coverage and out-of-pocket limits. If you would like a licensed agent to run your list against the plans we offer, you can request a quote, and it costs nothing to ask.
Leave yourself time. December 7 is a hard deadline for AEP, and a change made in the last days can leave little room to sort out a pharmacy or network question before January 1.
Your second chance: January 1 to March 31
If you are in a Medicare Advantage plan on January 1 and it is not working out, there is a second window. From January 1 through March 31, Medicare Advantage enrollees can make one change: switch to a different Medicare Advantage plan, or leave Medicare Advantage for Original Medicare and add a Part D drug plan.
That window is narrower than AEP. It allows only one change, and it is only for people already in a Medicare Advantage plan. It cannot be used to move from Original Medicare into Medicare Advantage, or to switch between standalone Part D plans. The Medigap caution above applies here too.
Outside both windows, you may qualify for a Special Enrollment Period after certain events, such as moving out of your plan's service area or your plan leaving your area.
Where to get help
This article is general information, not personalized advice. Medicare's own resources are free: you can compare every plan in your area at Medicare.gov, call 1-800-MEDICARE (1-800-633-4227), or get free one-on-one counseling from your State Health Insurance Assistance Program (SHIP). A licensed agent can also help you compare the plans they represent against your doctors, drugs and budget.
We do not offer every plan available in your area. Currently we represent 4 organizations which offer 1,172 products in your area. Please contact Medicare.gov, 1-800-MEDICARE, or your local State Health Insurance Program (SHIP) to get information on all of your options.