You enroll in Medicare once, but you may need to take action every year

You do not re-enroll in Medicare each year the way you might re-enroll in a workplace health plan. Once you are enrolled, you stay enrolled for life. However, Medicare gives you a window each year — called the Annual Enrollment Period — to change your coverage choices, switch plans, or add coverage you did not have before. If you do nothing during that window, your current plan continues into the next year.

The confusion arises because inaction has different meanings depending on which part of Medicare you use. If you are in Original Medicare (Parts A and B), doing nothing means you keep the same coverage. If you are in a Medicare Advantage plan or a prescription drug plan, doing nothing means you stay with that same plan — but that plan's costs, doctors, and drugs covered may change on January 1st. That is why many people take action during the enrollment period even though they do not have to re-enroll.

Key Takeaways

  • Medicare enrollment is permanent once you sign up; you do not re-enroll each year unless you choose to change plans.
  • The Annual Enrollment Period runs from October 15 to December 7 each year, and changes take effect January 1st.
  • If you take no action during the enrollment period, your current plan continues, but its costs and covered services may change.
  • You must take action if you want to switch from Original Medicare to Medicare Advantage, drop a prescription drug plan, or change plans within the same category.
  • Missing the Annual Enrollment Period usually means you cannot change plans until the next year, unless you have a may have access to life event.

What the Annual Enrollment Period is and when it happens

The Annual Enrollment Period (AEP) is the yearly window when you can change your Medicare coverage without penalty. It runs from October 15 through December 7 each year. Any changes you make during this period take effect on January 1st of the following year.

This period applies to everyone on Medicare, but the rules for what you can change depend on which type of coverage you have. If you are in Original Medicare with a Medigap plan, you can switch to a different Medigap plan or to Medicare Advantage. If you are in Medicare Advantage, you can switch to a different Medicare Advantage plan or back to Original Medicare. If you have a prescription drug plan, you can switch to a different one or drop it entirely.

There is also a separate Medicare Advantage Open Enrollment Period from January 1 to March 31 each year. During this time, if you are already in a Medicare Advantage plan, you can switch to a different Medicare Advantage plan or go back to Original Medicare — but you cannot switch into Medicare Advantage for the first time during this window.

What happens if you do nothing during the enrollment period

If you take no action during the Annual Enrollment Period, your current plan automatically renews for the next year. You will stay in the same plan with the same insurance company. However, this does not mean your costs stay the same. On January 1st, your plan's premiums, deductibles, copays, and the list of covered drugs or doctors may all change.

For example, a drug that your plan covered at no cost in 2024 might move to a higher cost tier in 2025, or a doctor you see regularly might leave the plan's network. You will not be notified of every change — the plan sends you an updated Summary of Benefits and Coverage, but many people do not read it. This is why reviewing your plan each year, even if you do not intend to switch, can save you money or prevent gaps in care.

If you are in Original Medicare without a Medigap or Medicare Advantage plan, inaction is simpler: you keep the same coverage with no changes to your enrollment status.

When you must take action to change plans

You must actively change your plan if you want to switch from one option to another. The most common switches are: moving from Original Medicare to Medicare Advantage, moving from Medicare Advantage back to Original Medicare, switching from one Medicare Advantage plan to another, or changing your prescription drug plan.

You can make these changes only during the Annual Enrollment Period (October 15 to December 7) or during the Medicare Advantage Open Enrollment Period (January 1 to March 31, if you are already in Medicare Advantage). If you miss both windows, you will be locked into your current plan for the rest of the year, with limited exceptions.

The exception is a may have access to life event — such as losing employer coverage, moving out of your plan's service area, getting married, or experiencing a death in the family. If you have a may have access to event, you can change plans within 60 days of the event, even outside the enrollment periods. You will need to report the event to Medicare and provide proof.

How to review and change your coverage

Start by reviewing your current plan's costs and coverage before the enrollment period begins. If you are in a Medicare Advantage or prescription drug plan, log into your plan's website or call the customer service number on your insurance card to see what is changing for next year. The plan must send you a notice of changes by September 30th each year.

If you want to compare other plans, use the Medicare Plan Finder tool on Medicare.gov. You can enter your medications, doctors, and hospitals to see which plans cover them and what your out-of-pocket costs would be. You can also call 1-800-MEDICARE to speak with someone who can walk you through your options.

Once you have decided to change plans, you can enroll during the Annual Enrollment Period by visiting Medicare.gov, calling 1-800-MEDICARE, or contacting the new plan directly. Changes take effect on January 1st. If you are switching from one plan to another, you do not need to do anything with your old plan — the new plan handles the transition.

Common mistakes to avoid during enrollment

The most common mistake is waiting until December to think about your coverage. By then, the enrollment period is nearly over, and you may rush into a decision. Start reviewing your options in September or early October.

Another mistake is assuming your plan costs nothing because you paid nothing last year. Medicare Advantage plans often have $0 premiums, but they have copays, coinsurance, and out-of-pocket maximums that vary by plan. A plan with a low premium might have high copays for your regular medications or doctors.

A third mistake is not checking whether your doctors and hospitals are in the network of a new plan you are considering. A plan might look cheaper on paper, but if your doctor is not in the network, you will pay more or have to switch providers. Always verify network status before enrolling.

Finally, do not assume you need to change plans every year. If your current plan still covers your needs and costs have not risen significantly, staying put is a valid choice. The goal is to find a plan that works for you, not to chase the lowest premium.

What to do if you missed the enrollment period

If the Annual Enrollment Period has passed and you did not change your plan, you are generally locked in until the next October 15th. However, there are a few exceptions.

If you are in a Medicare Advantage plan, you have until March 31st to switch to a different Medicare Advantage plan or back to Original Medicare. This is the Medicare Advantage Open Enrollment Period, and it applies only to people already in Medicare Advantage.

If you have a may have access to life event — such as losing health coverage, moving, getting married, or having a baby — you can request a Special Enrollment Period. You have 60 days from the event to change plans. You will need to contact Medicare at 1-800-MEDICARE or visit Medicare.gov to report the event and provide documentation.

Frequently Asked Questions

Do I have to enroll in Medicare Part D if I do not take prescription drugs?

You do not have to enroll in Part D if you do not take regular medications. However, if you go without Part D coverage for 63 days or more in a row, you may face a permanent late enrollment penalty when you do sign up. If you think you might need medications in the future, it is usually cheaper to enroll now and pay the premium than to pay the penalty later.

Can I switch from Medicare Advantage to Original Medicare outside the enrollment period?

You can switch from Medicare Advantage to Original Medicare during the Annual Enrollment Period (October 15 to December 7) or the Medicare Advantage Open Enrollment Period (January 1 to March 31). Outside these windows, you need a may have access to life event, such as moving out of your plan's service area or losing employer coverage.

What happens to my Medigap plan if I switch to Medicare Advantage?

Your Medigap plan will end when you switch to Medicare Advantage, since Medigap is designed to work with Original Medicare, not Medicare Advantage. If you later switch back to Original Medicare, you may be able to re-enroll in a Medigap plan, but you might not get the same plan or price you had before.

Will I be penalized if I do not change my plan during the enrollment period?

You will not be penalized for keeping your current plan. However, you will be penalized if you go without Part D coverage for more than 63 days in a row, or if you delay enrolling in Part B when you first become may be able to access. Staying in your current plan avoids these penalties.

How do I know if my doctor is in a plan's network?

Use the Medicare Plan Finder on Medicare.gov and enter your doctor's name, or call the insurance company directly and ask. Do not assume a doctor is in the network based on past coverage — networks change every year, and a doctor who was in your plan last year might not be in it next year.