You do not have to re-enroll in Original Medicare, but you must actively choose or change a Medicare Advantage or Part D plan every year during Open Enrollment

If you have Original Medicare (Part A and Part B), your coverage continues automatically year after year with no action required on your part. You pay your premiums, and you stay enrolled. However, if you have a Medicare Advantage plan (Part C) or a prescription drug plan (Part D), you must make a choice during the annual Open Enrollment period or your coverage may change in ways you do not expect.

The rules are different depending on which type of Medicare you have. Understanding which rule applies to you prevents gaps in coverage and unexpected costs.

Key Takeaways

  • Original Medicare (Part A and Part B) renews automatically each year without any action from you.
  • Medicare Advantage and Part D prescription drug plans end on December 31 each year and do not automatically renew — you must choose a plan during Open Enrollment or be switched to a default plan.
  • Medicare Open Enrollment runs from October 15 to December 7 each year, and your new coverage starts January 1.
  • If you miss Open Enrollment and do not have a may have access to life event, you cannot change plans until the next October.
  • You should review your plan each year even if you want to keep it, because drug formularies, provider networks, and premiums change.

Original Medicare automatically continues without re-enrollment

If you have Part A (hospital insurance) and Part B (medical insurance), you do not re-enroll. Your coverage straightforward continues. Medicare deducts your Part B premium from your Social Security check each month, and you remain covered as long as you pay.

You may receive a notice in the mail that looks like a renewal form, but it is informational only. You do not need to sign it, return it, or take any action. Your coverage is already active.

The only time you need to act is if you want to add coverage — for example, if you want to buy a Medigap supplemental plan or enroll in Part D for the first time. Those choices have their own important date and rules.

Medicare Advantage plans end each December 31 and require a new choice

Medicare Advantage (Part C) plans are offered by private insurance companies and include coverage of Part A, Part B, and usually Part D all in one plan. Unlike Original Medicare, these plans have a contract year that ends on December 31. Your plan does not automatically renew into the next year.

If you do nothing during Open Enrollment, Medicare will assign you to a default plan — usually a plan offered by the same company you are with, if one exists. This default plan may have different doctors, different costs, or different coverage than the plan you currently have. You may not discover the change until you try to see your doctor in January and learn they are no longer in the network.

To keep your current plan or switch to a different one, you must make an active choice during Open Enrollment. This choice is binding for the entire year ahead.

Part D prescription drug plans also require annual re-enrollment

If you have a standalone Part D plan (separate from Medicare Advantage), it also ends on December 31 and does not automatically renew. Drug formularies — the list of medications your plan covers — change every year. A drug you take today may move to a higher cost tier next year, or it may no longer be covered at all.

Even if you want to stay with the same insurance company, the plan you had last year may no longer be the best choice for your medications. You should review your current plan's formulary each October to see what is changing, then compare it to other plans available to you.

If you do not choose a plan during Open Enrollment, you will be automatically enrolled in a plan selected by Medicare. This plan may not cover your medications at all, or it may cover them at a much higher cost.

Medicare Open Enrollment: when and how to make your choice

Open Enrollment runs from October 15 through December 7 each year. This is the only time you can change Medicare Advantage or Part D plans without a may have access to life event. Your new coverage begins January 1.

You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, or by mail. You can also work with a licensed insurance agent or counselor. Many local Area Agencies on Aging offer free counseling during Open Enrollment to help you compare plans.

If you miss the December 7 important date, you cannot change plans until the next October — unless you experience a may have access to life event such as losing employer coverage, moving to a new state, or a death in your family. Some life events give you 60 days to make a change; others give you 30 days. The important date depends on the type of event.

What happens if you do not choose during Open Enrollment

If you have a Medicare Advantage or Part D plan and do nothing during Open Enrollment, you will be automatically enrolled in a plan for the next year. Medicare does not ask your permission — the enrollment happens automatically on January 1.

The plan you are assigned to may be offered by your current insurance company, but it is not necessarily the same plan you have now. It may have higher out-of-pocket costs, a smaller network of doctors, or different drug coverage. You will not know the details until after the enrollment period has closed and you cannot change your mind.

This is why reviewing your options during Open Enrollment is important, even if you think you want to keep your current plan.

Why you should review your plan every year, even if you keep it

Even if you decide to stay with your current Medicare Advantage or Part D plan, the plan itself changes every year. Premiums go up, doctor networks shrink, and drug formularies are updated. A plan that was the best choice for you last year may not be the best choice this year.

Set a reminder for early October to review your plan. Check whether your doctors are still in the network. Look at your prescription drugs and confirm they are still covered at the same cost tier. Compare your plan's premium, deductible, and out-of-pocket maximum to other plans available to you. The Medicare Plan Finder tool at Medicare.gov lets you enter your drugs and doctors to see which plans cover them.

If you find a better plan, you can switch during Open Enrollment. If you decide to stay, at least you made an informed choice rather than accepting whatever plan Medicare assigns to you by default.

Frequently Asked Questions

What if I turn 65 and enroll in Medicare for the first time — do I have to re-enroll next year?

If you enroll in Original Medicare for the first time, you do not re-enroll — your coverage continues automatically. If you enroll in Medicare Advantage or Part D for the first time, those plans end on December 31, and you must choose again during the next Open Enrollment period.

Can I change my Medicare plan outside of Open Enrollment?

Only if you have a may have access to life event, such as losing employer coverage, moving to a different state, getting married or divorced, or a death in your family. Some events give you 60 days to make a change; others give 30 days. Contact Medicare at 1-800-MEDICARE to report your event and ask about your important date.

What if I want to switch from Medicare Advantage back to Original Medicare?

You can switch during Open Enrollment (October 15 to December 7) without any penalty. If you switch, you may also want to enroll in a Medigap supplemental plan or a Part D drug plan at the same time, because Original Medicare does not cover everything. Some Medigap plans have limited enrollment periods, so act quickly.

If I miss Open Enrollment, what happens on January 1?

If you have Medicare Advantage or Part D and do nothing, you will be automatically enrolled in a plan selected by Medicare. This plan may be different from your current plan. If you have a may have access to life event within 60 days of missing the important date, you may still be able to make a change.

Where can I get help choosing a plan?

Medicare.gov has a Plan Finder tool where you can enter your doctors and medications to see which plans cover them. You can also call 1-800-MEDICARE for free counseling, or contact your local Area Agency on Aging to speak with a trained counselor at no cost.