Every fall, millions of people face the same question during the Annual Enrollment Period: stick with Medicare Advantage, or move to Original Medicare with a supplement? The decision feels routine, but one part of it is not reversible for everyone. Before you make a change for 2027, it helps to understand exactly what you are trading away and what door might close behind you.
Two Different Ways to Get Medicare
Original Medicare and Medicare Advantage are not just different price tags on the same product. They are two different systems for how your care gets approved and paid for.
Original Medicare Plus Medigap
Original Medicare is run directly by the federal government. You can see almost any doctor or hospital in the country that accepts Medicare, with no network to navigate. Many people pair it with a Medigap (Medicare Supplement) policy, which helps cover the cost-sharing Original Medicare leaves behind. This combination typically comes with a higher monthly premium, but it also comes with far less prior authorization. Most Original Medicare services do not require advance approval before you get care.
Medicare Advantage
Medicare Advantage bundles your hospital, medical, and usually drug coverage into one plan sold by a private insurer under contract with Medicare. In exchange for often lower premiums and extra benefits, you typically agree to use a network of providers, and many services require prior authorization before the plan will pay for them. That prior authorization step is where most Medicare Advantage denials come from. If a service is not approved in advance, or the plan decides it was not medically necessary, you can be left with a denial instead of a paid claim.
The Trade-Off Most People Already Know
Most comparisons stop here: Medicare Advantage costs less but has a network and gatekeeping; Original Medicare plus Medigap costs more but gives you freedom and fewer approval hurdles. That part is true. What gets missed is what happens if you choose Medicare Advantage now and later want to go back.
The Point Most Articles Miss: Switching Back May Not Be Easy
Leaving Medicare Advantage during the Annual Enrollment Period is simple. You pick Original Medicare, your request goes through, and your new coverage starts January 1. But picking up a Medigap policy to go along with it is a separate decision, governed by separate rules, and it is not guaranteed.
Most people have exactly one truly protected window to buy Medigap without health questions: a one-time Medigap open enrollment period, usually tied to when they first enroll in Medicare Part B. Outside that window, and outside a handful of limited guaranteed-issue situations defined by federal and state law, Medigap insurers in most states are allowed to use medical underwriting. That means an insurer can ask about your health, charge you more because of it, or decline your application outright.
This makes dropping Medicare Advantage to return to Original Medicare a potential one-way door. If you are healthy and your state's rules are generous, going back may be easy. If you have developed health conditions since you first enrolled, or your state offers only the federal minimum guaranteed-issue protections, an insurer could turn you down for a Medigap policy or price it out of reach. You would still have Original Medicare itself, since that is guaranteed, but you might be stuck without the supplement that makes Original Medicare affordable for many people.
A few states have chosen to be more generous than federal law requires, offering broader guaranteed-issue or underwriting protections. But which states, and what those protections look like, varies and changes. This article does not list them because the details depend on your state and can shift. Before you drop Medicare Advantage, you need to find out, in writing, whether you currently qualify for guaranteed issue in your state, or whether an application would be medically underwritten.
The bottom line: do this research before you leave Medicare Advantage, not after. Call your State Health Insurance Assistance Program, check with your state insurance department, or call 1-800-MEDICARE to confirm your guaranteed-issue status before you make a move you cannot easily undo.
How Appeals Work Differently in Each Program
Both Original Medicare and Medicare Advantage give you five levels of appeal if a claim or service is denied. The rights are real in both systems, but the names of the entities and the deadlines are not interchangeable.
Original Medicare Appeals
- Level 1 is a redetermination, filed within 120 calendar days from receipt of the notice (receipt is presumed to be 5 calendar days after the notice date unless shown otherwise).
- Level 2 goes to a Qualified Independent Contractor (QIC), filed within 180 calendar days from receipt of the redetermination notice.
Medicare Advantage Appeals
- Level 1 is a plan reconsideration, filed within 65 calendar days from the date on the notice itself, for both standard and expedited requests. This deadline runs from the notice date, not from when you received it, so there is no guessing about mail delivery.
- Level 2 is handled by the Independent Review Entity (IRE), currently MAXIMUS Federal Services. It is automatic: if your plan upholds its denial, the case is forwarded to the IRE without you having to file anything separately.
Levels 3, 4, and 5 Apply to Both Programs
- Level 3: an Administrative Law Judge hearing through OMHA, filed within 60 calendar days from receipt of the Level 2 decision.
- Level 4: review by the Medicare Appeals Council (Departmental Appeals Board), filed within 60 calendar days after receipt of the ALJ decision.
- Level 5: federal district court, filed within 60 calendar days after receipt of the Appeals Council decision.
Mixing these up matters. Applying Original Medicare's QIC to a Medicare Advantage case, or vice versa, will send your appeal to the wrong place. Keep your notice handy and match the deadline to the correct program.
Fast-Track Appeals When Coverage Is Ending
If you are in a skilled nursing facility, home health, or CORF setting and your Medicare Advantage plan says your covered services are ending, you can ask for a fast-track appeal through the BFCC-QIO. That request must reach the BFCC-QIO by noon of the day before the effective date on your Notice of Medicare Non-Coverage, and it can be made by phone or in writing. If the BFCC-QIO is closed due to an emergency, you get until noon the next business day it is open. Even if you miss the deadline, you keep your fast-track appeal rights and can still appeal after services end.
For an inpatient hospital discharge, the process is different. You must contact the BFCC-QIO by midnight of the day of discharge, before you leave the hospital. If you miss that window, you can still ask your Medicare Advantage plan for an expedited reconsideration. The notice explaining these rights is called the Important Message from Medicare. These two settings use different clocks, so don't apply one to the other.
Don't Give Up on a Denial
If you are denied a service, especially one requiring prior authorization, it is worth appealing. According to a 2024 KFF analysis, roughly 80% of appealed Medicare Advantage prior-authorization denials are overturned, though the same analysis found only about 11.5% of denied prior-authorization requests are actually appealed. That gap suggests many people who could win on appeal never try. Expedited Medicare Advantage reconsiderations, including those involving Part B drugs, must be decided within 72 hours; there is no shorter 24-hour exception at the appeal stage.
Know Your Enrollment Windows
The Annual Enrollment Period runs October 15 through December 7 each year, with changes effective January 1. For 2027 coverage, that means October 15 through December 7, 2026. Doing nothing during this window is not a neutral choice: if you take no action, you are generally renewed into your current plan under its new terms for the coming year. Plans must send you an Annual Notice of Change describing what is different, and it must arrive no later than September 30 before AEP begins, so September 30, 2026 for 2027 coverage.
If you are already in a Medicare Advantage plan on January 1, you also get a second chance: the Medicare Advantage Open Enrollment Period, running January 1 through March 31. This lets you make one change, either to a different MA plan or back to Original Medicare. It is not a second AEP. It is open only to people already in Medicare Advantage, allows just one election, and new coverage starts the first day of the month after your request is received.
There is also a narrower Special Enrollment Period for 5-star plans, usable once per contract year from December 8 before the contract year through November 30 of that year, but only if a 5-star-rated plan is actually available where you live.
Why Your Coverage Can Change Even If You Don't
Prior-authorization rules, formularies, and provider networks reset every plan year on January 1. A service your plan covered without question last year can require prior authorization, or get denied, this year, even though nothing about your health changed. That is why reviewing your Annual Notice of Change carefully matters, even if you plan to stay put.
If you are already mid-treatment when you join a new Medicare Advantage plan, or new to Medicare altogether, the plan must give you a transition period of at least 90 days during which it cannot disrupt your active course of treatment or demand reauthorization, even if your provider is out of network. An approval already in hand for a course of treatment also stays valid as long as that treatment remains medically necessary. Ask your plan in writing exactly how it will handle your specific situation, since at least 90 days is a floor, not a ceiling on the protection.
Checking Your Paperwork
Original Medicare enrollees receive a Medicare Summary Notice. Medicare Advantage enrollees do not; instead, their plan sends an Explanation of Benefits, and any denial arrives as a Notice of Denial of Medical Coverage or Payment, also called the Integrated Denial Notice. Know which one applies to you, and keep every notice you receive, since deadlines are often tied to the date printed on it.
Because rules, dates, and dollar amounts can change, always confirm current details at Medicare.gov or by calling 1-800-MEDICARE before making your final decision for 2027.
FAQ
Can I switch from Medicare Advantage back to Original Medicare anytime?
You can switch back to Original Medicare during the Annual Enrollment Period (October 15 through December 7) or, if you are already in a Medicare Advantage plan, during the Medicare Advantage Open Enrollment Period (January 1 through March 31). Getting Original Medicare itself is always guaranteed, but adding a Medigap policy afterward is a separate question governed by your state's underwriting rules.
Will I automatically be able to get a Medigap policy if I leave Medicare Advantage?
Not necessarily. Outside your one-time Medigap open enrollment window and limited guaranteed-issue situations, insurers in most states may use medical underwriting and can decline your application or charge more based on your health. A few states are more generous, so check your own state's rules and your guaranteed-issue status before dropping Medicare Advantage.
What is the deadline to appeal a Medicare Advantage denial?
A Medicare Advantage Level 1 appeal, called a plan reconsideration, must be filed within 65 calendar days from the date on the notice, for both standard and expedited requests. If the plan upholds its denial, the case is automatically forwarded to the Independent Review Entity (IRE) for Level 2, with no separate filing needed.
How is appealing an Original Medicare denial different from appealing a Medicare Advantage denial?
Original Medicare's Level 1 appeal is called a redetermination, filed within 120 calendar days from receipt of the notice, and Level 2 goes to a Qualified Independent Contractor (QIC) within 180 calendar days from receipt. Medicare Advantage's Level 1 appeal is a plan reconsideration filed within 65 calendar days from the notice date, and Level 2 goes automatically to the Independent Review Entity (IRE), not a QIC.
Is it worth appealing a Medicare Advantage prior-authorization denial?
Often yes. A 2024 KFF analysis found that roughly 80% of appealed Medicare Advantage prior-authorization denials are overturned, yet only about 11.5% of denied prior-authorization requests are actually appealed. That gap suggests it is worth pursuing an appeal rather than accepting a denial outright.
What happens if I do nothing during the Annual Enrollment Period?
Doing nothing is not a neutral choice. If you take no action during the Annual Enrollment Period (October 15 through December 7, effective January 1), you are generally renewed into your current plan under its new plan-year terms, which can include different costs, networks, or prior-authorization rules.
Denied? You don't have to fight alone.
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This article is general education, not legal or medical advice. Medicare rules, deadlines, and dollar amounts change; confirm the current details for your situation at Medicare.gov or by calling 1-800-MEDICARE. MedicareClaimDenied.com is not affiliated with or endorsed by Medicare, CMS, or any insurer.