November 1, 2026 · Medicare · By Pioneer Eagle

Medicare’s Annual Enrollment Period, Explained Plainly

Every autumn, Medicare gives you one window to change how you get your coverage for the coming year. It is called the Annual Enrollment Period — sometimes shortened to AEP — and it runs from October 15 through December 7. Changes you make during those weeks take effect on January 1.

The mailbox fills up, the television ads get loud, and a lot of folks simply throw up their hands and let last year’s plan roll over. Sometimes that is fine. Sometimes it quietly costs real money, because plans change their prices, their doctor networks, and their drug lists every single year. This article walks through what the enrollment period is, what you can and cannot change during it, and the mistakes we see families make most often.

What you CAN change during October 15 – December 7

• Switch from Original Medicare (Parts A and B, usually with a Part D drug plan) to a Medicare Advantage plan (Part C) — or the other way around.
• Switch from one Medicare Advantage plan to another.
• Switch from one Part D prescription drug plan to another, join a Part D plan if you do not have one, or drop Part D coverage.
• If you are in a Medicare Advantage plan and later regret it, there is a second, smaller window — the Medicare Advantage Open Enrollment Period, January 1 to March 31 — when you can switch Advantage plans once, or go back to Original Medicare and pick up a Part D plan.

What you generally CANNOT do in the fall window

• Sign up for Medicare for the very first time. First-time enrollment has its own window, around your 65th birthday (or when you retire and lose employer coverage). The fall period is for people who already have Medicare.
• Freely buy a Medigap (supplement) policy. This surprises people. Outside your one-time Medigap open enrollment window at 65 — and a few special situations — an insurer can generally ask health questions and can decline you or charge more. Leaving Medicare Advantage to return to Original Medicare does not automatically come with a right to a Medigap policy. If you are thinking about that switch, check your Medigap options before you make it, not after.

The one letter worth reading: your Annual Notice of Change

Every September, your current plan mails an Annual Notice of Change. Most people throw it in the recycling. Please don’t. It lists exactly what is changing in your plan next year: the monthly premium, the deductible, whether your doctors are still in the network, and whether your prescriptions are still covered at the same price. Ten minutes with that letter tells you whether standing pat is safe or expensive.

Five common mistakes

1. Choosing by premium alone. The cheapest monthly premium can come with the most expensive prescriptions. Compare the total yearly cost — premium plus what you will actually pay for your specific drugs and doctors. Medicare.gov’s Plan Finder does this math with your real medication list, and it is free.
2. Not checking your doctors. Networks change every year. Confirm your primary doctor, your specialists, and your hospital are in the plan’s network for next year, not this one.
3. Not checking your drugs. Enter your exact prescriptions, dosages, and pharmacy into the Plan Finder. A plan that covers your neighbor’s pills cheaply may price yours in a higher tier.
4. Missing December 7. After the 7th, your choices generally lock until the next fall (special circumstances aside). If December sneaks up on you, you will live with the old plan another year.
5. Taking enrollment advice from an advertisement. The person on television is selling a plan. For free, unbiased help, call your state’s SHIP program (State Health Insurance Assistance Program) — trained counselors who do not sell anything — or use Medicare.gov and 1-800-MEDICARE.

A calm way to handle the season

1. Read the Annual Notice of Change when it arrives in September.
2. Make a list: your doctors, your hospital, your prescriptions with dosages.
3. Run that list through Medicare.gov’s Plan Finder, or sit down with a SHIP counselor.
4. Compare two or three plans on total yearly cost — not premium, not advertising.
5. Make any change well before December 7, and keep the confirmation letter or number.
6. Write the new plan’s name and start date on the family calendar, so everybody who helps with care knows which card to use in January.

Next in this series: how to read the Medicare & You handbook without your eyes glazing over.