Medicare · 6 min read
Medicare Open Enrollment, Oct 15 to Dec 7: Three Things to Re-Check Before You Do Nothing
Retirement Made Clear editorial
Reviewed by Theo Halbardier, CFP®, CIMA®, CAIA®, The Financial Sciences Company
Reviewed
Published
Medicare’s Open Enrollment Period runs October 15 through December 7, and changes take effect January 1. If you do nothing, your current Medicare Advantage or Part D plan usually renews with whatever changes its insurer filed for next year — listed in the Annual Notice of Change your plan mailed by September 30. Before December 7, re-check three things: whether your drugs are still covered and on what tier, whether your doctors and hospitals are still in network, and what a bad year would cost under the new premium, deductible, and out-of-pocket limit. This is an educational summary of the rules, not advice.
Every fall, Medicare gives you seven and a half weeks to change your coverage for next year — and most people spend them doing nothing. That is not always a mistake. But “nothing” is itself a choice: if you take no action, your current plan usually renews on January 1 with whatever changes its insurer filed for the new year. The window exists so you can check those changes before they arrive.
The Window: October 15 to December 7
Medicare’s Open Enrollment Period runs from October 15 through December 7 every year. Inside it you can join, drop, or switch a Medicare Advantage plan; move from Original Medicare to Advantage or back; and join, drop, or switch a Part D drug plan. Whatever you choose takes effect January 1, as long as the plan receives your request by December 7. (Medicare.gov, joining a plan, accessed October 5, 2026; 42 C.F.R. §422.62(a)(2) and §423.38(b).)
Your plan has already told you what is changing. Medicare Advantage and Part D plans must send an Annual Notice of Change by September 30 — the letter that lists next year’s premium, deductible, drug list, and network changes. If it went in a drawer, it is the first thing to find.
| Window | Dates | Who can use it | What you can do |
|---|---|---|---|
| Open Enrollment | Oct 15 – Dec 7 | Everyone with Medicare | Switch Advantage or drug plans; move between Original Medicare and Advantage. Effective Jan 1. |
| Medicare Advantage Open Enrollment | Jan 1 – Mar 31 | People already in an Advantage plan | One switch to another Advantage plan, or back to Original Medicare (and add a drug plan). |
| Medigap Open Enrollment | 6 months from Part B, once | People new to Part B | Buy any Medigap policy with no health questions. Fall Open Enrollment does not reopen this. |
(Medicare.gov, joining a plan; CMS and NAIC, Choosing a Medigap Policy, March 2026.)
The Three Things to Re-Check
Plans change their terms every year, and three changes do most of the damage. Each takes a few minutes with your Annual Notice of Change and Medicare’s Plan Finder.
1. Your drugs: still covered, and on what tier?
A drug plan’s formulary — its list of covered drugs — can change for the new year. A medication can drop off the list, move to a more expensive tier, or pick up a prior-authorization or quantity rule. Enter every prescription you take, at its actual dose, into Plan Finder and compare next year’s cost across plans, including your preferred pharmacy.
One figure caps the downside: in 2026, once you have paid $2,100 out of pocket for covered Part D drugs, you pay nothing more for covered drugs for the rest of the year. The cap is adjusted every year; your plan’s notice shows next year’s figure. (CMS, 2026 Medicare Advantage and Part D Rate Announcement, April 7, 2025.)
2. Your doctors and hospitals: still in the network?
Medicare Advantage plans work through networks, and networks change. A doctor, a specialist, or the hospital system you rely on can leave a plan for the new year. Call the offices that matter to you and ask directly whether they will be in-network with your plan next year — directories lag. Original Medicare has no network: any provider that takes Medicare takes you, which is part of what its higher out-of-pocket exposure buys.
3. Your costs: premium, deductible, and the out-of-pocket ceiling
Look past the monthly premium. A $0-premium plan can carry a higher deductible, higher copays, or a higher maximum out-of-pocket limit than it did this year. Add up what a bad year would cost — the premium times twelve plus the plan’s out-of-pocket maximum — and compare that number, not just the premium, across plans. Your Part B premium, $202.90 a month in 2026, is owed either way and does not change with the plan you pick. (CMS, 2026 Medicare Parts A & B Premiums and Deductibles.)
If You Miss December 7
If you are in a Medicare Advantage plan, you get one more chance: from January 1 through March 31 you can make one switch to another Advantage plan or return to Original Medicare and pick up a drug plan. If you are on Original Medicare with a stand-alone drug plan, that second window does not apply to you. Outside these windows, changes generally require a Special Enrollment Period — a move, losing other coverage, or a few other qualifying events.
What This Does Not Mean
None of this says you should switch. Many people re-check, find their plan still fits, and keep it — which is a fine result. And none of it says Medicare Advantage or Original Medicare is the better choice; that turns on your health, your doctors, where you live, and how much cost uncertainty you can live with. The window governs when you can change, not whether you should.
Frequently Asked Questions
Q: When is Medicare open enrollment?
October 15 through December 7 every year. Changes you make take effect January 1, as long as the plan receives your request by December 7.
Q: What happens if I do nothing during open enrollment?
In most cases your current Medicare Advantage or Part D plan renews automatically on January 1, with whatever premium, drug list, and network changes it filed for the new year. Your Annual Notice of Change, mailed by September 30, lists them.
Q: Can I switch Medigap policies during open enrollment?
Fall open enrollment does not create a Medigap right. Outside your one-time six-month Medigap window, most states let insurers ask health questions and decline you, unless a guaranteed-issue right applies.
Q: I missed December 7. Can I still change plans?
If you are in a Medicare Advantage plan, yes: from January 1 to March 31 you can make one switch to another Advantage plan or return to Original Medicare. Otherwise, changes generally need a Special Enrollment Period.
The decisions in this guide are what the Retirement Checkup™ scores — seven questions, two minutes, no email needed to see your score.
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General educational information, current as of 2026. Not personalized investment, tax, or legal advice — figures and rules change. For guidance specific to your situation, talk to a qualified professional. See our disclosures.