You Don't Have to Re-Enroll in Original Medicare, But You Do Need to Act During Open enrollment if You Want to Change Plans
If you have Original Medicare (Part A and Part B), you stay enrolled automatically year to year — there is no re-enrollment step. Your coverage continues unless you cancel it. However, 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 and decide whether to keep your current plan or switch. Even if you do nothing, your plan renews, but your costs, covered drugs, and network doctors may change.
The key distinction is this: Original Medicare is "set it and forget it" once you are enrolled. Private plans (Advantage and drug plans) require an annual decision point. Missing that window means you are locked into your current plan for the full year, even if your costs go up or your doctor leaves the network.
Key Takeaways
- Original Medicare Part A and Part B renew automatically each year with no action required on your part.
- Medicare Advantage and Part D drug plans renew automatically but their costs and coverage change yearly, so you should review them during open enrollment.
- Open enrollment runs from October 15 to December 7 each year, and changes take effect January 1.
- If you miss open enrollment and want to switch plans, you may have to wait until the next year unless you experience a may have access to life event.
- You can switch Original Medicare to a Medigap supplemental plan at any time, but switching from Medigap back to Advantage may be harder and more expensive.
How Original Medicare Renewal Works
Original Medicare Part A and Part B do not require you to re-enroll or take any action each year. Once you are enrolled — usually at age 65 or when you become may be able to access due to disability or end-stage renal disease — your coverage renews automatically on January 1 of each year. Your premiums may change, and Medicare will notify you of any adjustments, but you do not need to sign anything or confirm your enrollment.
Your Part A premium is usually zero if you or your spouse paid Medicare taxes for at least 10 years. Your Part B premium is deducted from your Social Security check each month, and if it increases, you will see the new amount on your Social Security statement or in a letter from Medicare. You can change your Part B premium payment method or opt out of Part B, but that requires a separate request — it is not part of an annual re-enrollment process.
Medicare Advantage and Drug Plan Open Enrollment
If you are enrolled in a Medicare Advantage plan or a Part D prescription drug plan, your plan automatically renews each January 1, but you have a window each fall to change plans or drop coverage. This window is called Open Enrollment for Medicare Advantage and Part D, and it runs from October 15 to December 7 each year. During this period, you can switch to a different Advantage plan, switch to Original Medicare, add or change a drug plan, or drop coverage entirely.
If you do not make a change during this window, your current plan renews automatically. This matters because plan details shift year to year: your copays may increase, your deductible may change, your doctor or pharmacy may leave the network, or the plan may add or remove covered drugs. You will receive a notice in the mail (usually in September or early October) showing what is changing in your plan for the coming year. That notice is your signal to review whether your plan still fits your needs.
If you miss the October 15 to December 7 window and want to switch plans, you generally cannot do so until the next year's open enrollment — unless you experience a may have access to life event such as losing employer coverage, moving out of your plan's service area, or becoming newly may be able to access for Medicaid.
What Happens If You Switch from Original Medicare to Advantage
You can move from Original Medicare to a Medicare Advantage plan during open enrollment, and the switch takes effect January 1. However, switching back from Advantage to Original Medicare is more complicated. You have the right to return to Original Medicare during open enrollment, but if you want to buy a Medigap supplemental policy at the same time, you may face higher premiums or coverage exclusions because insurers can deny coverage or charge more based on your health history.
The exception is if you are switching back within your first year of Advantage enrollment — in that case, you have a may provide right to buy a Medigap policy without medical underwriting. After that window closes, Medigap insurers can use medical underwriting, meaning they can charge you more or refuse to cover you if you have pre-existing conditions. This is why the decision to leave Original Medicare for Advantage should be made carefully: returning to Original Medicare later may be more expensive.
important date and Timing for Changes
| Action | Window | When It Takes Effect |
|---|---|---|
| Switch Advantage or drug plans, or switch to Original Medicare | October 15 – December 7 | January 1 |
| Switch back to Original Medicare from Advantage (may provide Medigap access) | First 12 months after Advantage enrollment | First of the month after request |
| Make changes due to may have access to life event | Within 60 days of the event | Varies by event and plan |
| Disenroll from Part B or Part A | Anytime (no window) | Month after request |
How to Review Your Coverage Before Open Enrollment
Start reviewing your plans in September, before open enrollment begins. Log into Medicare.gov and use the "Plan Finder" tool. Enter your current plans, the drugs you take, and your preferred doctors and pharmacies. The tool will show you what your out-of-pocket costs would be under each available plan in your area for the coming year. Compare your current plan's costs to alternatives.
Check whether your doctors and pharmacies are still in-network for your current plan. Plans change their networks every year, and a doctor you see regularly may no longer be covered. If your doctor is leaving your plan, that is a strong reason to switch. Also review the formulary — the list of covered drugs — for any changes to your prescriptions. Some plans add drugs to their formulary or move drugs to a higher cost tier.
If you need help comparing plans, you can call 1-800-MEDICARE (1-800-633-4227) and speak with a counselor, or contact your local State Health Insurance information Program (SHIP), which offers free, unbiased plan counseling. Have your current plan documents and a list of your medications and doctors ready when you call.
What Happens If You Miss the important date
If open enrollment ends on December 7 and you have not made a change, your current plan renews automatically for the next year. You are locked in until the next open enrollment period (October 15 to December 7 of the following year), unless you experience a may have access to life event.
may have access to life events include losing employer coverage, moving out of your plan's service area, becoming newly may be able to access for Medicaid, getting married or divorced, or having a significant change in income. If any of these happen, you have 60 days from the event to request a plan change, and the change usually takes effect the first of the month after your request. You will need to provide proof of the life event — such as a letter from your employer, a lease showing your new address, or a marriage certificate.
Frequently Asked Questions
Do I have to do anything if I want to keep my current plan?
No. Your plan renews automatically on January 1. You do not need to re-enroll or take any action to stay in your current plan. However, you should still review the notice your plan sends you in September or October to see what costs or coverage are changing.
What if my doctor left my Medicare Advantage plan's network?
If your doctor is no longer in-network, that is a may have access to reason to switch plans outside of open enrollment. Contact your plan or call Medicare at 1-800-633-4227 to request a plan change. You will need to provide proof that your doctor is no longer in-network, such as a letter from the doctor's office or a screenshot from the plan's website.
Can I switch from Original Medicare to Advantage anytime, or only during open enrollment?
You can switch to Advantage only during open enrollment (October 15 to December 7) or if you have a may have access to life event. You cannot switch to Advantage in the middle of the year unless your circumstances change in a way Medicare recognizes.
If I switch plans in December, when does my new plan start?
Any plan changes you make between October 15 and December 7 take effect on January 1 of the following year. Your current plan covers you through December 31, and your new plan begins January 1.
What if I want to drop Medicare Advantage and go back to Original Medicare?
You can switch back to Original Medicare during open enrollment. If you also want to buy a Medigap policy, you have may provide access to coverage without medical underwriting only during your first 12 months in Advantage. After that, Medigap insurers can deny you or charge more based on your health.