Medicare Advantage vs Medigap: The Choice You Make at 65 That Gets Harder to Undo

At a glance: Both paths start with Medicare Part A and Part B — then they split. Medicare Advantage (Part C) hands your benefits to a private plan: a network of doctors, copays as you go, an extra premium averaging $14 a month (CMS, 2026) that can be $0, and a legal ceiling on your worst year — at most $9,250 in-network in 2026 (CMS). Original Medicare + Medigap keeps Medicare itself in charge: any provider in America who takes Medicare, and a Plan G policy that pays nearly every cost Medicare leaves behind — everything except the $283 Part B deductible (CMS, 2026). The catch is the door: you can move into an Advantage plan every fall, but coming back to Medigap usually means passing a medical exam. Guaranteed windows: the 6 months after Part B starts, plus two 12-month trial rights. Rules and 2026 figures checked October 25, 2026.

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Some Medicare decisions repeat every year. This one doesn't — not cleanly. CMS projected roughly 34 million people would be in Medicare Advantage in 2026, and every one of them, plus everyone turning 65 this fall, faces the same fork: pay more each month to see almost any doctor with almost no bills afterward, or pay little or nothing extra and accept a network, copays, and permission slips. Both choices are reasonable. Choosing the second one without knowing it can become permanent is not. This guide prices both paths, then shows you the rules of the door between them.

Two paths from the same starting line

Whichever way you go, you first enroll in Part A and Part B and keep paying the Part B premium — $202.90 a month in 2026 (CMS):

	Original Medicare + Medigap + Part D	Medicare Advantage (Part C)
Who runs your coverage	Medicare itself; Medigap pays Medicare's leftovers	A private plan, paid by Medicare to run your benefits
Extra monthly premium	Medigap premium (varies by state, age, company) + a Part D premium (CMS's 2026 average: $34.50)	Plan premium — CMS's 2026 average is $14.00; many plans charge $0
Your doctors	Any doctor or hospital in the U.S. that accepts Medicare	The plan's network — HMOs usually require staying in-network; PPOs charge more outside it
Referrals & approvals	No referrals; prior authorization is rare	Referrals common in HMOs; prior authorization required for some services in 99% of plans (KFF)
Your worst year	No cap in Original Medicare itself — but Plan G leaves you only the $283 Part B deductible	Capped by law: at most $9,250 in-network in 2026; $13,900 combined for PPOs (CMS)
Prescription drugs	A separate Part D plan (2026 drug cap: $2,100)	Usually built into the plan (same $2,100 cap)
Dental, vision, hearing, fitness	Not covered by Original Medicare or Medigap	Most plans add some of these extras (CMS)
Care outside the U.S.	Plan G pays 80% of emergency care abroad (after a $250 deductible, $50,000 lifetime limit)	Emergency care is covered anywhere in the U.S.; abroad, most plans pay little or nothing
Can you hold both?	No — a Medigap policy cannot be sold to someone in an Advantage plan (Medicare.gov)	No — Medigap cannot pay Advantage costs

One row matters most: an Advantage plan must cover everything Original Medicare covers (HHS OIG). What changes is not the service list — it is who decides, where you may go, and how you pay your share.

The one-way door: why this choice is different

Every fall, anyone with Medicare can join an Advantage plan for January 1 — no health questions, ever. Leaving is just as easy: disenroll, and Original Medicare takes you back automatically. What does not come back automatically is the Medigap policy. That asymmetry is the whole story.

When you first take Part B at 65 or older, a 6-month Medigap Open Enrollment Period starts (Medicare.gov). Inside it, insurers must sell you any policy they offer in your state, whatever your health. Our turning-65 enrollment guide walks that window month by month. After it closes, in most states an insurer may medically underwrite you: read your history, charge more for it, or refuse outright. Medicare's own guide is blunt — after the window, "there's no guarantee that an insurance company will sell you a Medigap policy if you don't meet their medical underwriting requirements" (Choosing a Medigap Policy, CMS). A heart condition or a cancer history can end the conversation — and the people most likely to want Medigap later are the least likely to pass the exam.

Two federal escape hatches exist, and both run on a 12-month clock:

• The at-65 trial right. Joined an Advantage plan when you first became eligible for Part A at 65? Switch back within the first 12 months and you may buy any Medigap policy sold in your state, guaranteed issue (Medicare.gov; CMS).
• The dropped-Medigap trial right. Dropped a Medigap policy to try an Advantage plan for the first time? Switch back within 12 months and you can have your old policy back if the company still sells it — or, if it doesn't, one of the guaranteed-issue letters (Plan A, B, K or L; those first eligible in 2020 or later get Plan D or G in place of the retired C and F).

Either way, the Medigap application itself has a deadline inside the deadline: apply no earlier than 60 days before your Advantage coverage ends and no later than 63 days after (Medicare.gov). Other guaranteed-issue rights exist (a plan leaving your area, for instance) but offer the limited letter set, not any policy. A few states add protections of their own; your State Insurance Department or SHIP can tell you yours. The federal floor is this: after month 12, your health becomes the price of the Medigap door.

The money: cheap years, expensive years, and the 20-year shape

Compare the two most common Medigap choices in Plan G vs Plan N.

Start with why Medigap exists at all. Original Medicare alone has no limit on what you pay: after the $283 deductible you owe 20% of most Part B bills, forever. On $30,000 of Part B services — one year of outpatient cancer care, say — that is $6,226.40 out of your pocket, and the same again next year. Plan G deletes that exposure: it pays the Part A deductible ($1,736 in 2026), all Part A and Part B coinsurance, skilled-nursing coinsurance, even Part B excess charges — everything except the $283 deductible (Medicare.gov's Medigap chart). Income surcharges ride on top of both paths; our IRMAA brackets guide prices them.

The same choice, as three kinds of year (2026 figures):

The year	Advantage path costs you	Medigap path costs you
Premiums alone (CMS averages)	$202.90 Part B + $14.00 plan = $2,602.80/yr	$202.90 Part B + Medigap + $34.50 Part D — Plan G premiums vary widely; priced in the example below
A healthy year	Premiums + small copays	Premiums + $0–$283
The worst legal year	Premiums + up to $9,250 (in-network ceiling; the average enrollee's plan caps near $5,421 — CMS landscape data)	Premiums + $283

Stretch premiums across 20 years, holding today's prices flat just to see the shape: the Advantage path's premiums total roughly $48,700–$52,100; a Medigap path with a mid-priced Plan G totals roughly $96,600 (the example below shows its build). That ~$45,000 gap is what the Medigap path charges for certainty. But Advantage copays in ordinary years claw some of it back, Medigap premiums typically climb with age, and one ceiling year in an Advantage plan ($6,573 worse than the same year on Plan G) erases about 2¾ years of the premium savings. Neither path wins in the abstract. They win in your years, with your doctors.

The prior-authorization divide

The difference people feel most is not the copay. It is the permission step. In Original Medicare, prior authorization applies to a short list of services: KFF counted about 2 requests per 100 beneficiaries in 2024. In Medicare Advantage, 99% of enrollees are in plans that require prior authorization for some services — hospital stays, skilled nursing, chemotherapy among the most common — and insurers made 52.8 million determinations in 2024 (KFF, from data insurers report to CMS). Of those, 4.1 million (7.7%) were denied in full or in part.

Two findings keep this honest rather than scary. First, most people never fight: only 11.5% of denials were appealed — yet 80.7% of appeals were overturned, in whole or in part. Second, the federal watchdog found real error inside the system: reviewing denials at 15 of the largest Advantage organizations, the HHS Office of Inspector General estimated 13% of prior-authorization denials were for services that met Medicare's own coverage rules — care that "likely would have been approved" under Original Medicare — and 18% of payment denials met both Medicare coverage rules and the plans' billing rules. Most requests are approved. But the Advantage path asks something of you the Medigap path does not: a willingness to appeal, with your doctor's office, when the first answer is no.

Meet Diane: one hospital year, priced both ways

(Labelled hypothetical. Premiums use CMS's 2026 Part B premium and Part D average plus an illustrative mid-range Plan G premium; Advantage copays are illustrative in-network figures in the range plans commonly set. Your plan's Evidence of Coverage is the only real price list.)

Diane, 67, spends 4 days in the hospital, then sees specialists 10 times and does 8 physical-therapy visits in the year.

	Original Medicare + Plan G + Part D	$0-premium Advantage plan
Monthly premiums	$202.90 Part B + $165 Plan G + $34.50 Part D = $402.40	$202.90 Part B + $0 = $202.90
Her hospital stay	$1,736 Part A deductible → Plan G pays it	$395/day × 4 days = $1,580
Specialists + therapy	20% coinsurance → Plan G pays it	$45 × 10 + $25 × 8 = $650
She pays at the point of care	$283 (the year's Part B deductible — the one gap Plan G leaves)	$2,230
Total for the year	$5,111.80	$4,664.80

Read that table twice, because it refuses to behave. In Diane's hospital year — a genuinely expensive year — the Advantage path still comes out $447.00 cheaper, because the Medigap path's premiums are that much higher. The Medigap path wins a different year: the catastrophic one, where Advantage cost-sharing runs to its ceiling while Plan G's bill stays $283. That is the actual trade: Medigap charges about $2,394 a year (in this example) to convert unknown five-figure risk into a known $283. Advantage charges nothing for the conversion — and keeps the risk, capped, on your side of the table.

The free one-page MA vs Medigap Decision Worksheet prices your own two paths side by side, with the six questions that actually decide this. Get the free worksheet (PDF) → or have it sent to your inbox →.

Who each path fits

Your situation	The path that usually fits	Why
You travel for months, or split the year between two homes	Medigap	Any Medicare provider in any state works; an Advantage network stays home when you don't
Your specialists are chosen, trusted, and non-negotiable	Medigap	No network list can retire your cardiologist; no referral stands between you and her
You're healthy, your doctors are in a strong local plan, and the premium matters most	Advantage	$0–$14 extra a month, extras included, and the cap still guards the worst year
A serious diagnosis would send you to a famous center across the state — or across the country	Medigap	Centers of excellence are simply "in network" when the network is Medicare itself
You live where Advantage networks are thin — few plans, one hospital system	Medigap (check first)	A $0 premium buys little where the network is a desert; CMS counts 10+ choices for 97% of beneficiaries, which means 3% have far fewer
The bundled extras — dental, vision, hearing, fitness — carry real dollar value for you	Advantage	Original Medicare and Medigap exclude routine dental, vision and hearing entirely

Notice what is not on this table: "sick people" versus "healthy people." Health argues both ways: the sick value Medigap's open door and predictable bills, and they also meet Advantage ceilings and prior-auth desks more often. The deciders are geography, doctors, and how much uncertainty your budget can hold.

If you switch: the mechanics

• Into an Advantage plan, or between plans: the fall Open Enrollment, October 15 – December 7, for coverage starting January 1 — our Open Enrollment mistakes guide covers the traps; check your doctors and drugs first.
• Already in an Advantage plan? The Medicare Advantage Open Enrollment Period, January 1 – March 31, allows one switch — to another Advantage plan, or back to Original Medicare with a Part D plan.
• Back to Medigap: the underwriting warning applies at the moment you disenroll, not after. If a trial right or guaranteed-issue right covers you, apply for the Medigap policy first (up to 60 days before your Advantage coverage ends), keep every plan letter, and treat the 63-day clock as your deadline.

The decision checklist

1. List your doctors and hospital. Check each against the Advantage plan's 2027 network — in writing, from the plan, not the brochure.

2. Price your worst year, not your average one. Advantage: premium × 12 + the plan's out-of-pocket maximum. Medigap: premiums × 12 + $283. Compare those two numbers first.

3. Check your calendar rights. Inside the 6-month Medigap window, or a 12-month trial right? Write the end date down.

4. Map your travel. Months away from home each year is a network question before it is a money question.

5. Count the extras honestly — what would dental, vision, hearing and fitness cost you without the plan's versions?

6. Decide how you'll handle a "no." If prior authorization denies a service, will you appeal? The overturn rate says appealing works — but somebody has to do it.

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Run your own numbers before December 7: the free MA vs Medigap Decision Worksheet puts both paths' premiums, caps and totals on one printable page, with the six decision questions and the trial-right dates to fill in. Get the free worksheet (PDF) → or have it emailed to you →. Every worksheet this desk publishes lives on our Worksheets page.

Frequently asked questions

Can I have Medigap and Medicare Advantage at the same time?

No. Medigap only works with Original Medicare, it cannot pay any Advantage cost, and it is illegal for anyone to sell you a Medigap policy while you are enrolled in an Advantage plan (Medicare.gov). If two premiums are leaving your account, one is buying nothing.

Is the $0 premium real?

Yes, and incomplete. You always keep paying the Part B premium ($202.90 a month in 2026). Beyond that, many Advantage plans charge $0 — CMS's average across all Advantage plans is $14.00 — because Medicare pays the plan directly to run your care. What you pay instead arrives as copays when you use care, up to your plan's yearly maximum.

I have been in an Advantage plan for three years and my health changed. Can I get Medigap now?

You can apply — but outside the trial rights and other guaranteed-issue situations, in most states the insurer may medically underwrite you: health questions, higher prices, or a decline. A few states add protections, so check with your State Insurance Department or SHIP before assuming either answer.

What exactly is the trial right?

A one-time, 12-month undo. If you joined an Advantage plan when you first became eligible at 65, switching back within 12 months lets you buy any Medigap policy sold in your state, guaranteed. If you dropped a Medigap policy to try Advantage for the first time, switching back within 12 months restores your old policy if it is still sold, or a guaranteed-issue letter if it is not.

Does Medigap cover my prescriptions, dental, or a nursing home?

No to all three: drugs need a Part D plan on the Medigap path, routine dental/vision/hearing are excluded from Original Medicare and Medigap alike, and neither pays for long-term custodial care. Advantage plans are the only one of the three that routinely bundle dental, vision and hearing extras.

Which path do most people choose?

Advantage — CMS projected about 34 million enrollees for 2026, close to half of everyone with Medicare. Popularity is information about premiums and marketing, not about fit: the right answer is the one whose network contains your doctors and whose worst year your savings can survive.

Sources & official figures

• Centers for Medicare & Medicaid Services — 2026 Medicare Parts A & B Premiums and Deductibles fact sheet (November 14, 2025; opened October 25, 2026): standard Part B premium $202.90; Part B deductible $283; Part A inpatient deductible $1,736 per benefit period: https://www.cms.gov/newsroom/fact-sheets/2026-medicare-parts-b-premiums-deductibles
• CMS — Medicare Advantage and Medicare Prescription Drug Programs Expected to Remain Stable in 2026 (press release, September 26, 2025; opened October 25, 2026): average Advantage premium $14.00 in 2026; average stand-alone Part D premium $34.50; average Part D premium inside Advantage plans $11.50; enrollment projected at 34 million; 97% of beneficiaries have 10 or more plan choices; supplemental offerings "such as hearing, dental, and vision" remain stable: https://www.cms.gov/newsroom/press-releases/medicare-advantage-medicare-prescription-drug-programs-expected-remain-stable-2026
• Medicare.gov — When can I buy a Medigap policy? (opened October 25, 2026): the Medigap Open Enrollment Period is "the 6-month period that starts the first day of the month you're 65 or older and signed up for Part B"; guaranteed issue — any policy sold in your state (at-65 trial right), your prior policy back or Plan A, B, K or L (dropped-Medigap right), applications 60 days before to 63 days after coverage ends; "It's illegal for someone to sell you a Medigap policy if you have a Medicare Advantage Plan": https://www.medicare.gov/health-drug-plans/medigap/ready-to-buy/when
• Medicare.gov — Compare Medigap plan benefits (opened October 25, 2026): Plan G covers the Part A deductible, Part A and Part B coinsurance, excess charges, skilled-nursing coinsurance and the first 3 pints of blood — every listed benefit except the Part B deductible; foreign-travel emergency pays 80% for Plans C, D, F, G, M and N: https://www.medicare.gov/supplements-other-insurance/how-to-compare-medigap-policies
• U.S. Department of Health and Human Services, Office of Inspector General — Some Medicare Advantage Organization Denials of Prior Authorization Requests Raise Concerns About Beneficiary Access to Medically Necessary Care (OEI-09-18-00260, April 2022; report opened October 25, 2026): among denials at 15 of the largest Advantage organizations (one week of June 2019), an estimated 13% of prior-authorization denials met Medicare coverage rules and 18% of payment denials met Medicare coverage and billing rules; plans "may impose additional requirements… requiring prior authorization… or requiring referrals": https://oig.hhs.gov/oei/reports/OEI-09-18-00260.pdf
• KFF — Medicare Advantage Insurers Made Nearly 53 Million Prior Authorization Determinations in 2024 (January 28, 2026; opened October 25, 2026): 99% of Advantage enrollees must obtain prior authorization for some services; 52.8 million determinations in 2024; 4.1 million (7.7%) denied; 11.5% of denials appealed; 80.7% of appeals partially or fully overturned; traditional Medicare submitted just over 625,000 requests (about 2 per 100 beneficiaries): https://www.kff.org/medicare/issue-brief/use-of-prior-authorization-in-medicare-advantage-exceeded-46-million-requests-in-2022

Last updated: October 25, 2026 — checked against CMS, Medicare.gov, HHS OIG and KFF sources on October 25, 2026.

Disclaimer: The Retirement Desk publishes education, not insurance, financial, or legal advice, and sells no plans. Diane is a labelled hypothetical; her Plan G premium and Advantage copays are illustrative, and real premiums and copays vary by state, plan, and year. Your state's Medigap rules may add protections beyond the federal floor — confirm yours with your State Insurance Department, your SHIP, or 1-800-MEDICARE before a deadline, not after.

Filed under: Medicare — The Retirement Desk, the situation-first retirement money desk for Americans 60–75.