Medicare Open Enrollment: Dates and What You Can Change
Once a year, Medicare gives you a window to change your coverage — and once a year, most people let it pass without checking whether their plan still fits. Plans change their costs, drug lists, and networks every year; the plan that was perfect last January may not be this fall. Here are the dates that matter, exactly what you can change in each window, and how to decide whether to act — so you're not locked into the wrong plan for a year.
Quick answer
Medicare's fall Open Enrollment (the Annual Enrollment Period) runs October 15 to December 7 every year, and changes you make take effect January 1. During it you can switch between Original Medicare and Medicare Advantage, change or drop a Medicare Advantage plan, and join, switch, or drop a Part D drug plan. A separate Medicare Advantage Open Enrollment Period (January 1–March 31) lets people already in an Advantage plan make one change. Verify everything against Medicare.gov before you act.
When is Medicare open enrollment?
The main window — Medicare's Annual Enrollment Period, which most people call open enrollment — runs October 15 through December 7 every year. Any change you make during it takes effect January 1 of the following year. That's the window to review your coverage and switch if a better fit exists.
A plain-English guide, not legal or financial advice
This article explains how these rules generally work so you can ask better questions — it isn't legal, financial, or tax advice, and the details vary. For your own situation, check the primary sources linked below and, where it matters, work with a qualified attorney or advisor.
What you can change during open enrollment (Oct 15 – Dec 7)
- Switch from Original Medicare to a Medicare Advantage plan — or from Medicare Advantage back to Original Medicare.
- Change or drop your Medicare Advantage plan for a different one.
- Join, switch, or drop a Part D prescription drug plan.
This is the once-a-year chance to make these moves for most people. If you do nothing, your current plan generally renews — but at next year's costs and with next year's drug list and network, which may have changed.
The Medicare Advantage window (Jan 1 – Mar 31)
There's a second, narrower window. The Medicare Advantage Open Enrollment Period runs January 1 to March 31, and it's only for people already enrolled in a Medicare Advantage plan. It allows one change: switch to a different Advantage plan, or drop Advantage and return to Original Medicare (and pick up a Part D plan). You can't use it to join Medicare Advantage for the first time. Changes take effect the first day of the month after the plan gets your request.
If you missed signing up for Medicare entirely
The General Enrollment Period (January 1–March 31) is different again — it's for people who didn't sign up for Part A and/or Part B when they were first eligible. If that's you, our guide on the pre-retirement countdown covers avoiding the late-enrollment penalty, and the enrollment calendar tool maps your exact dates.
How to decide whether to switch
Open enrollment isn't a prompt to change — it's a prompt to check. Each fall your plan mails an Annual Notice of Change; read it. The three things most likely to have moved:
- Your drugs — is every prescription still covered, and at what tier? This is the most common reason to switch a Part D or Advantage plan.
- Your doctors — for Advantage plans, are your doctors and preferred hospital still in network for next year?
- The total cost — premiums, deductibles, and copays, not just the headline premium. The cheapest premium isn't always the cheapest plan.
If you're timing this alongside the move from work coverage to Medicare at 65, our guide on health insurance before Medicare and the Medicare enrollment calendar map the deadlines so nothing slips.
You may be interested in…
Health Insurance for the Early Retiree
Retired before 65? This book walks early retirees through bridging coverage until Medicare starts — pricing every option so you don't overpay in the gap.
Emergency Binder
Once you pick a plan, keep the card where you can reach it. The Emergency Binder holds your Medicare details, doctors, and medications in one place.
Medicare Organizer
Open enrollment means comparing plans, drugs, and doctors side by side. The Medicare Organizer gives you fill-in pages to line them all up before you choose.
Start getting retirement in order — one simple checklist at a time
Free quick-start checklists to help you organize the practical parts of retirement: what to gather, what to decide, and what to write down first.
- What to gather
- What to update
- What to share with family
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Good to know
Common questions
When is Medicare open enrollment 2026?
The fall Annual Enrollment Period runs October 15 to December 7, 2026, with changes taking effect January 1, 2027. These are the same fixed dates every year. The separate Medicare Advantage Open Enrollment Period runs January 1 to March 31, 2026. Always confirm at Medicare.gov.
What is the Medicare open enrollment deadline?
December 7 is the deadline for the fall Annual Enrollment Period — changes made by then take effect January 1. If you're already in a Medicare Advantage plan and miss it, the Medicare Advantage Open Enrollment Period (January 1–March 31) gives you one more chance to make a single change.
What can I change during Medicare open enrollment?
During the October 15–December 7 window you can switch between Original Medicare and Medicare Advantage, change or drop your Medicare Advantage plan, and join, switch, or drop a Part D prescription drug plan. It's the once-a-year opportunity for most people to make these moves.
What happens if I do nothing during open enrollment?
Your current plan generally renews automatically — but at next year's costs, drug list, and provider network, which can change. Read the Annual Notice of Change your plan sends each fall; if your drugs, doctors, or total costs have shifted, open enrollment is your window to switch.
What's the difference between the fall period and the January–March window?
The fall Annual Enrollment Period (Oct 15–Dec 7) is open to everyone with Medicare and allows several kinds of changes. The Medicare Advantage Open Enrollment Period (Jan 1–Mar 31) is only for people already in an Advantage plan and allows just one change. A third window, the General Enrollment Period (also Jan 1–Mar 31), is for people who never signed up for Part A/B when first eligible.
Don't miss your window
Map your exact Medicare dates
The free Medicare Enrollment Calendar turns your birthday and situation into the specific enrollment windows and deadlines that apply to you — so open enrollment and your Initial Enrollment Period never catch you off guard.
Open the Medicare Enrollment Calendar →