You can change Medicare plans during specific windows each year, and the timing depends on which type of plan you have

Medicare sets annual periods when you can switch plans without penalty. If you have Original Medicare (Parts A and B), you can change to a Medicare Advantage plan or switch between Advantage plans during the Annual Enrollment Period. If you already have a Medicare Advantage or Part D prescription plan, you have multiple chances to change — some windows are short (as little as two weeks), and others last several weeks. Missing a important date usually means you are locked into your current plan until the next enrollment period opens.

The rules are different for each type of change you want to make. Switching from Original Medicare to Advantage is not the same as switching between two Advantage plans, and adding or changing prescription coverage has its own calendar. Understanding which window applies to your situation saves you from being stuck with a plan that no longer fits your needs.

Key Takeaways

  • The Annual Enrollment Period runs October 15 through December 7 each year and is when most people can change any Medicare plan.
  • If you have a Medicare Advantage plan, you also get the Medicare Advantage Open Enrollment Period from January 1 through March 31 to switch to a different Advantage plan or back to Original Medicare.
  • Changes made during October through December take effect January 1 of the following year.
  • Special enrollment periods open outside the regular windows if you move, lose coverage, or experience certain life changes — you must report the change within 60 days.
  • Switching back from Medicare Advantage to Original Medicare is permanent for that year; you cannot switch back to Advantage until the next Annual Enrollment Period.

The Annual Enrollment Period: October 15 through December 7

The Annual Enrollment Period is the main window when you can change any Medicare plan. It runs from October 15 through December 7 each year. During this time, you can switch from Original Medicare to a Medicare Advantage plan, change from one Advantage plan to another, add or change a Part D prescription plan, or add a Medigap supplemental plan. Any change you make during this window takes effect on January 1 of the next year.

This is the longest and most flexible enrollment window Medicare offers. If you are unhappy with your current plan's costs, coverage, or network of doctors, this is when you have the most options. You can compare plans online through Medicare.gov, call 1-800-MEDICARE, or meet with a counselor at your local Area Agency on Aging. Many people use this period to review whether their current plan still matches their health needs and prescription medications.

The Medicare Advantage Open Enrollment Period: January 1 through March 31

If you are already enrolled in a Medicare Advantage plan, you get a second chance to change plans during the Medicare Advantage Open Enrollment Period, which runs January 1 through March 31 each year. During this window, you can switch to a different Medicare Advantage plan or switch back to Original Medicare. You cannot use this period to add a Medigap plan or change prescription coverage — those changes must wait for the October Annual Enrollment Period.

This period exists because people sometimes discover after January 1 that their new Advantage plan does not work as expected. A doctor may not be in the network, a medication may not be covered, or costs may be higher than anticipated. The January-through-March window gives you a chance to correct that choice. However, switching back to Original Medicare during this period is permanent — you cannot switch back to an Advantage plan until October.

Special Enrollment Periods: When You Can Change Outside Regular Windows

Life changes can open enrollment windows outside the regular calendar. If you move to a new state or county, lose employer coverage, get married or divorced, or experience other may have access to events, you may be able to change plans when ready. Medicare calls these Special Enrollment Periods. The key requirement is that you report the change to Medicare within 60 days of when it happens.

Common may have access to events include moving out of your plan's service area, losing Medicaid, losing retiree health coverage from a former employer, becoming a U.S. citizen or legal resident, or having a family member move in or out of your home. You will need to provide documentation — a lease or utility bill for a move, a letter from your employer for loss of coverage, or a marriage certificate for a name change. Contact Medicare at 1-800-MEDICARE or your local Social Security office to report the change and find out which plans you can switch to.

Switching from Original Medicare to Advantage: What Happens

If you currently have Original Medicare and want to switch to a Medicare Advantage plan, you can do so during the Annual Enrollment Period (October 15 through December 7). Your new Advantage plan coverage begins January 1. You do not need to do anything to drop Original Medicare — it ends automatically when your Advantage plan starts.

Before you switch, check whether your current doctors and hospitals are in the Advantage plan's network. Advantage plans often have smaller networks than Original Medicare, and switching means you may lose access to your current providers. You also lose the flexibility of Original Medicare, which accepts all doctors who accept Medicare. If you have a Medigap supplemental plan, you will lose that coverage when you switch to Advantage, and you may not be able to get it back at the same price if you switch back to Original Medicare later.

Switching from Advantage Back to Original Medicare

You can switch from a Medicare Advantage plan back to Original Medicare during the Annual Enrollment Period (October 15 through December 7) or during the Medicare Advantage Open Enrollment Period (January 1 through March 31). The change takes effect on January 1 if you switch during the fall, or within a few days if you switch during the January-March window.

Once you switch back to Original Medicare, you cannot switch to an Advantage plan again until the next Annual Enrollment Period in October. This is a one-way door for the rest of the year. If you are thinking about switching back, consider whether you will want to rejoin an Advantage plan later — if you might, it is better to wait and make the change during October when you have more time to decide. You can also enroll in a Medigap plan or Part D prescription plan when you switch back to Original Medicare, though you may want to do this at the same time to avoid gaps in coverage.

Changing Prescription Drug Coverage

You can change your Part D prescription plan during the Annual Enrollment Period (October 15 through December 7). If you are in a Medicare Advantage plan that includes prescription coverage, you can also change that coverage during the Medicare Advantage Open Enrollment Period (January 1 through March 31). Changes take effect January 1 if made in the fall, or shortly after if made in the winter.

Prescription coverage changes are important to review each year because drug formularies (the list of covered medications) change, and new generic versions of medications may become available. If your current plan no longer covers a medication you take, or if the cost has gone up significantly, the enrollment periods give you a chance to switch to a plan with better coverage for your specific drugs. You can use the Medicare Plan Finder tool on Medicare.gov to see which plans cover your medications and at what cost.

What Happens If You Miss an Enrollment Window

If you miss the Annual Enrollment Period and do not have a may have access to life change, you are locked into your current plan until the next October. You cannot switch plans, add coverage, or make changes. The only exception is if you are in a Medicare Advantage plan — you still have the January 1 through March 31 window to make one change.

If you realize too late that you need to change plans, contact Medicare at 1-800-MEDICARE to ask whether a Special Enrollment Period applies to your situation. Sometimes people may have access to without realizing it — for example, if you moved and did not report it, or if you lost coverage and did not know you had 60 days to report it. It is worth asking, because the rules have exceptions that are not always obvious.

Frequently Asked Questions

Can I change plans if I just realized my doctor is not in my plan's network?

Yes, during the Annual Enrollment Period (October 15 through December 7) or, if you have an Advantage plan, during the January 1 through March 31 window. If you are outside these periods and your doctor recently left the network, contact Medicare to ask whether you may have access to for a Special Enrollment Period — sometimes a network change triggers one.

What if I switch back to Original Medicare and then change my mind?

You cannot switch back to a Medicare Advantage plan until the next Annual Enrollment Period in October. This is permanent for the rest of the year. Before you switch back, make sure you are ready to stay in Original Medicare for at least several months.

Do I lose my Medigap plan if I switch to Medicare Advantage?

Yes. Medigap plans work only with Original Medicare, not with Advantage plans. If you switch to Advantage, your Medigap coverage ends. If you later switch back to Original Medicare, you may be able to enroll in a Medigap plan again, but the price may be higher than what you paid before.

Can I change plans more than once during the Annual Enrollment Period?

Yes. You can make multiple changes during October 15 through December 7, but only your final choice will take effect on January 1. If you change your mind, just make another change before December 7 ends.

What counts as a may have access to life change for a Special Enrollment Period?

Moving to a new state or county, losing employer coverage, getting married or divorced, becoming a U.S. citizen, losing Medicaid, and having a family member move in or out are common examples. You must report the change within 60 days. Contact Medicare at 1-800-MEDICARE to confirm whether your situation qualifies.