You do not have to re-enroll in Original Medicare, but you must act during Open Enrollment if you want to switch plans or change your coverage

Original Medicare (Part A and Part B) stays active year to year without any action on your part — once you are enrolled, you stay enrolled. But if you have a Medicare Advantage plan (Part C) or a prescription drug plan (Part D), you must review your coverage each year during the Open Enrollment Period, which runs from October 15 to December 7. If you do nothing during this window and want to change plans, you will be locked into your current coverage for the rest of the year.

The confusion happens because "re-enroll" means different things. You do not have to submit new paperwork to keep Medicare itself. But the insurance market changes every year — plans add and drop coverage areas, change their drug formularies, adjust copays, and alter their networks. Open Enrollment exists so you can respond to those changes. Missing it does not cancel your coverage; it just means you cannot switch until the next year.

Key Takeaways

  • Original Medicare (Part A and Part B) continues automatically each year with no action required from you.
  • Medicare Advantage and Part D prescription drug plans require you to review and confirm your coverage during Open Enrollment (October 15 to December 7) each year, or you stay in your current plan.
  • If you miss Open Enrollment and want to switch plans, you must wait until the next year unless a may have access to life event occurs.
  • Changes you make during Open Enrollment take effect on January 1 of the following year.
  • If you turn 65 and enroll in Medicare for the first time, you have an Initial Enrollment Period of seven months, not an annual one.

How Original Medicare stays active without annual re-enrollment

Part A (hospital insurance) and Part B (medical insurance) do not require you to take any step each year to keep them. Once you turn 65 and enroll — or once you become may be able to access through disability or end-stage renal disease — your coverage renews automatically on January 1 each year. You will receive a new Medicare card in the mail, usually in September or October before the year changes, but this is a formality, not a re-enrollment step.

Your premiums may change from year to year. Medicare announces the new Part B premium in the fall, and Social Security automatically deducts it from your benefit check each month. If you pay Part A premiums (which applies only if you do not have 40 work credits), those also renew without action on your part. The same applies to any Part B premium surcharge you owe based on your income.

The only reason your Original Medicare coverage would end is if you request it in writing or if you lose citizenship. Inactivity does not cancel it.

Open Enrollment for Medicare Advantage and Part D plans

If you have a Medicare Advantage plan (which replaces Original Medicare and is run by a private insurer) or a standalone Part D prescription drug plan, you must take action during Open Enrollment if you want to change plans. The Open Enrollment Period runs from October 15 to December 7 each year. During this window, you can switch to a different Medicare Advantage plan, drop Medicare Advantage and return to Original Medicare, add a Part D plan, or switch to a different Part D plan.

If you do nothing during Open Enrollment, your current plan automatically renews for the next year. You will stay in that plan for the entire calendar year unless a may have access to life event — such as moving out of the plan's service area, losing other health coverage, or experiencing a death in the family — occurs. These events trigger a Special Enrollment Period, which allows you to change plans outside the annual window.

Changes you make during Open Enrollment take effect on January 1. If you submit a change on November 1, it does not take effect until January 1 of the next year. Plans do not process mid-year switches except in cases of may have access to events.

What happens if you miss Open Enrollment

Missing the October 15 to December 7 window means you cannot change your Medicare Advantage or Part D plan until the next year's Open Enrollment Period arrives. If your current plan is dropping coverage in your area, raising copays significantly, or no longer covers a drug you take, you are still locked in unless you have a may have access to event.

A may have access to event is a specific life change that Medicare recognizes as a reason to let you switch outside the normal window. These include moving to a new state or county, losing employer coverage, getting married or divorced, having a baby, or experiencing the death of a spouse. If any of these happen to you, you typically have 60 days to make a change. You will need to contact your plan or Medicare directly to report the event and request a Special Enrollment Period.

If you miss Open Enrollment and have no may have access to event, your only option is to wait. You cannot switch plans, add coverage, or drop coverage until October 15 of the following year.

Initial Enrollment Period for people turning 65

If you are turning 65 for the first time, you have a different enrollment window called the Initial Enrollment Period. This runs for seven months: three months before the month you turn 65, the month you turn 65, and three months after. During this window, you enroll in Original Medicare or Medicare Advantage for the first time. This is not an annual re-enrollment; it is a one-time entry into the program.

Once your Initial Enrollment Period ends, you enter the regular Medicare system. From that point forward, Original Medicare continues without action, but Medicare Advantage and Part D plans follow the annual Open Enrollment schedule.

If you delay enrolling past your Initial Enrollment Period and do not have a may have access to reason (such as employer coverage), you may face a permanent penalty on your premiums. This is why getting the timing right at 65 matters more than in later years.

When you must act even outside Open Enrollment

A few situations force you to take action outside the normal Open Enrollment Period. If your plan is leaving the Medicare market entirely, Medicare will send you a notice and give you a Special Enrollment Period to choose a new plan. If you move out of your plan's service area, you can switch. If you lose other health coverage — such as retiree coverage from a former employer — you have 60 days to enroll in a Medicare plan.

If you are in a Medicare Advantage plan and you need to see a doctor outside your plan's network, you cannot straightforward switch plans mid-year. Instead, you would need to wait for Open Enrollment or establish that you have a may have access to event. This is why checking your plan's network and drug formulary during Open Enrollment is important — you are making a choice that will lock you in for the full year.

How to prepare for Open Enrollment

Start reviewing your coverage in September, before Open Enrollment begins on October 15. Pull together a list of the medications you take and the doctors you see. Check whether your current plan still covers those drugs and whether your doctors are still in-network. Medicare.gov has a plan comparison tool where you can enter your drugs and doctors and see which plans cover them.

If you are in Original Medicare with a standalone Part D plan, check whether your plan is still available and whether the copays or deductible have changed. If you are in a Medicare Advantage plan, verify that your primary care doctor is still in-network and that any specialists you use are covered. Many people find that their plan's network shrinks or their copays rise, and Open Enrollment is the only time to respond without penalty.

Write down the dates: Open Enrollment runs October 15 to December 7. Changes take effect January 1. If you wait until December 8, you will be locked in for another year.

Frequently Asked Questions

Do I have to do anything to keep my Original Medicare coverage?

No. Part A and Part B renew automatically each year. You do not need to submit forms, call Medicare, or take any action. Your coverage continues as long as you remain a U.S. citizen and do not request to cancel it.

What happens if I do nothing during Open Enrollment?

Your current Medicare Advantage or Part D plan automatically renews for the next calendar year. You stay in that plan for the full year unless you experience a may have access to life event that triggers a Special Enrollment Period.

Can I switch Medicare plans in January?

No. Open Enrollment ends on December 7, and changes take effect on January 1. If you miss the important date, you cannot switch until the next Open Enrollment Period in October, unless you have a may have access to event.

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

Moving to a new state or county, losing other health coverage, getting married or divorced, having a baby, or experiencing a death in the family all may have access to. You typically have 60 days from the event to make a change. Contact Medicare or your plan to report the event.

Do I need to re-enroll in Medicare when I turn 66 or 67?

No. Once you enroll during your Initial Enrollment Period at 65, you do not re-enroll at any later age. Original Medicare continues automatically. Medicare Advantage and Part D plans follow the annual Open Enrollment schedule, but that is not a re-enrollment — it is an optional review and change window.