People on Medicare get one set window each fall to rework their coverage for the year ahead, and a plan chosen once and left alone can quietly turn expensive if premiums rise or a pharmacy drops out of the network. This year’s window opens October 15 and runs through December 7, and the choice made — or not made — in those weeks decides what a household pays for premiums, prescriptions and doctor visits starting January 1.
The rules sound straightforward, but two separate enrollment periods get mixed up every year: a fall window open to nearly everyone with Medicare, and a second, narrower window in the new year that only some people can use. Confusing the two, or missing the December 7 cutoff on the first one, can mean being locked into the same plan for another 12 months.
The October 15 to December 7 Window, and Why January 1 Is a Hard Line
The Medicare Open Enrollment Period runs from October 15 through December 7 every year, according to Medicare.gov. Any change made inside that window takes effect January 1 of the following year, but only if the plan receives the enrollment request by December 7 — a request that arrives December 8 or later does not count, even if it was mailed earlier in the month.
That hard stop matters because the window is not a grace period; it is the only chance most people get all year to walk away from a plan that raised its premium, narrowed its drug formulary, or dropped a preferred doctor from its network. Outside this window and a handful of special circumstances, a Medicare Advantage or Part D plan is locked in for the full calendar year.
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What Can Actually Change During This Window
During the fall Open Enrollment Period, a person with Medicare can join, drop or switch a Medicare Advantage Plan with or without drug coverage, add or drop drug coverage on an existing Medicare Advantage Plan, switch from Original Medicare to a Medicare Advantage Plan or back again, and join, drop or switch a stand-alone Part D drug plan while staying on Original Medicare. To drop drug coverage specifically, Medicare.gov lists several accepted methods: calling 1-800-MEDICARE, mailing or faxing a signed written notice to the plan, submitting a request online if the plan offers that option, or asking the plan to send a disenrollment notice to complete and return.
A household does not need to submit a request at all if the current plan still fits. Silence is treated as a decision to stay, and the same plan carries forward into the new year automatically, as long as the plan itself is not leaving the Medicare program or the person’s area.
A Second, Narrower Window Opens January 1 — But Not for Everyone
A separate period, the Medicare Advantage Open Enrollment Period, runs January 1 through March 31 each year. It is easy to confuse with the fall window because both involve switching plans, but the two differ in who can use them, what they allow and when the change takes effect. The enrollment-period table on Medicare.gov spells out the distinction: the January-through-March window is open only to people already enrolled in a Medicare Advantage Plan, it permits a single change rather than the open menu available in the fall, and that change is limited to switching to a different Medicare Advantage Plan or dropping Medicare Advantage altogether to return to Original Medicare, with the option to add a separate Part D plan.
Timing also works differently between the two periods. A fall Open Enrollment change always starts January 1, no matter when in the six-and-a-half-week window the request goes in. A change made during the January-to-March period instead takes effect on the first of the month after the plan receives the request — so a switch made in February starts March 1, not at the start of the year. Someone who is not currently on a Medicare Advantage Plan cannot use this second window at all; it does not offer a way to join Medicare Advantage for the first time or to move off a stand-alone Part D plan.
The Medigap Catch That Trips Up a Plan Switch
Anyone who moves from a Medicare Advantage Plan back to Original Medicare, in either window, often assumes a Medicare Supplement Insurance policy, known as Medigap, will simply be available to fill the coverage gaps. That is not guaranteed. Under the federal rules explained on Medicare.gov’s Medigap eligibility guide, the clearest federal right to buy any Medigap policy sold in a state, regardless of health history, comes during a one-time six-month window that starts the first day of the month someone is 65 or older and enrolled in Part B. Outside that window, and outside a short list of qualifying situations such as a plan leaving Medicare or a move out of a plan’s service area, insurers generally are not required to sell a Medigap policy, and an application can be turned down or priced higher based on health history.
That means switching back to Original Medicare during the fall or spring window does not, by itself, restore Medigap access. A household considering the move is better served checking its specific situation against Medicare’s guaranteed-issue rules, or a State Health Insurance Assistance Program counselor, before assuming supplemental coverage will be there to catch a gap in Original Medicare’s cost-sharing.
What Happens if No One Acts
The default outcome of doing nothing during the fall window is not chaos — it is continuation. A current Medicare Advantage or Part D plan rolls forward into the new year without any paperwork, as long as the plan is still offered where the person lives. What does not stay the same is the price: premiums, deductibles and covered drug lists are set fresh by each plan for the coming year, so a household that changes nothing can still see its costs move. The only way to compare what a plan will actually charge in the coming year, rather than assume it matches the one just ending, is to review the new terms before December 7 rather than after.
This article was produced with AI assistance and reviewed by a human editor. Figures are linked to their primary sources; where a claim could not be verified from the public record, we say so.
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