Medicare Open Enrollment is the annual window from October 15 through December 7 when anyone with Medicare can change their coverage for the following year. Any changes you make during this period take effect on January 1. Outside of this window, your Medicare plan choices are essentially locked in, with a few narrow exceptions.
What You Can Change During Open Enrollment
The fall Open Enrollment Period is the most flexible time of year for Medicare beneficiaries. You can make any of the following moves:
- Switch from Original Medicare to a Medicare Advantage plan (or the reverse)
- Change from one Medicare Advantage plan to another, with or without drug coverage
- Join, switch, or drop a Part D prescription drug plan if you’re in Original Medicare
- Add or remove drug coverage from your Medicare Advantage plan
You only get one change during this period, and the last enrollment action you take before December 7 is the one that counts. If you’re happy with your current plan, you don’t need to do anything. Your existing coverage renews automatically.
What You Can’t Change During This Period
One common source of confusion: the fall Open Enrollment Period does not apply to Medigap (Medicare Supplement) policies. Medigap has its own separate enrollment window, a six-month period that begins the first month you’re both 65 or older and enrolled in Part B. During that six-month window, insurers must sell you a policy regardless of your health. After it closes, there’s no federal guarantee that a company will sell you a Medigap policy at all, and if one does, it can charge more based on your health history.
The fall enrollment period also isn’t the time to sign up for Medicare itself. Initial enrollment in Part A and Part B happens around your 65th birthday through a separate process.
The January Through March Enrollment Period
There’s a second, more limited window from January 1 through March 31 called the Medicare Advantage Open Enrollment Period. This one is only available if you’re already in a Medicare Advantage plan. During these months, you can switch to a different Medicare Advantage plan or drop your Advantage plan to return to Original Medicare (and pick up a standalone Part D drug plan if you want one).
What you can’t do during January through March: switch from Original Medicare into a Medicare Advantage plan. That move is reserved for the fall period. Think of the January window as a second chance for people who aren’t happy with the Advantage plan they chose in the fall.
Why Reviewing Your Plan Each Year Matters
Medicare plans change their costs, covered drugs, and provider networks every year. A plan that worked well for you this year might drop a medication from its formulary, raise its copays, or remove your preferred doctors next year. Plans are required to send you an “Annual Notice of Change” each September detailing what’s different for the coming year, and that document is worth reading carefully.
Prescription drug coverage is where annual reviews pay off most. Even if your medications haven’t changed, the plan’s pricing for those specific drugs may have shifted. Switching to a plan that better covers your prescriptions can save hundreds of dollars over the course of a year.
For Medicare Advantage enrollees, the average monthly premium in 2025 is about $13, and 76% of enrollees pay no plan premium beyond their standard Part B premium. But premiums tell only part of the story. Out-of-pocket limits, specialist copays, and network restrictions vary widely between plans. Two plans with identical premiums can cost you very different amounts depending on the care you actually use.
The Part D Out-of-Pocket Cap
A major recent change affects anyone with Medicare drug coverage. Starting in 2025, there’s a hard cap on what you pay out of pocket for prescription drugs each year. Once your spending reaches the limit, you pay nothing for covered Part D drugs for the rest of the calendar year. Previously, beneficiaries in the “catastrophic coverage” phase still owed a percentage of drug costs with no ceiling, which could mean thousands of dollars for people on expensive medications.
This cap makes it especially important to compare Part D plans during Open Enrollment. Plans still differ in their deductibles, copay structures, and which drugs they cover, but the annual ceiling means no plan can leave you exposed to unlimited costs the way older plans could.
Late Enrollment Penalties
If you delay signing up for Part D drug coverage and go 63 days or more without “creditable” drug coverage (meaning coverage at least as good as Medicare’s), you’ll face a permanent penalty when you do enroll. The penalty adds 1% of the national base beneficiary premium for every month you were uncovered. That might sound small, but it compounds. Someone who went 14 months without creditable coverage would pay an extra $5.50 per month in 2026, on top of their regular premium, for as long as they have Part D.
The penalty resets each year based on the current national base premium ($38.99 in 2026), so the dollar amount can rise over time even though the percentage stays fixed. This is a lifetime surcharge, not a one-time fee, which is why most people are better off enrolling in drug coverage as soon as they’re eligible, even if they don’t currently take expensive medications.
Special Enrollment Periods Outside the Fall Window
Certain life events unlock a Special Enrollment Period that lets you make changes outside the standard October-to-December window. Qualifying events typically include moving out of your plan’s service area, losing employer-sponsored coverage, qualifying for Medicaid, or entering a nursing facility. Each event opens a limited window (often two months) to adjust your coverage.
One Special Enrollment Period is available year-round with no qualifying life event: you can switch to any Medicare Advantage or Part D plan that has earned a 5-star quality rating from Medicare. Five-star plans represent the highest-rated options in your area, and Medicare allows you to join one at any time during the year.
How to Compare Plans
The Medicare Plan Finder tool at medicare.gov lets you enter your medications, preferred pharmacies, and doctors to see which plans in your area offer the best combination of cost and coverage. You’ll need your Medicare number and a list of your current prescriptions, including dosages.
State Health Insurance Assistance Programs (SHIPs) offer free, personalized counseling to help you compare options. Every state has one, and the counselors are trained specifically in Medicare. They can walk you through the Plan Finder results or help you understand what an Annual Notice of Change means for your specific situation. You can find your local SHIP by calling 1-877-839-2675.