Medicare Advantage vs. Medigap Supplement: The Decision Most Seniors Get Wrong

By Rodney Cummings, RSSA® | Legacy Wealth Services

Every year, hundreds of thousands of seniors turning 65 face what sounds like a simple choice: Medicare Advantage or a Medigap Supplement plan?

Insurance companies spend billions of dollars in advertising to make the answer seem obvious. The commercials show smiling retirees getting dental, vision, hearing, and gym memberships — all for $0 a month. It looks like a no-brainer.

But for many seniors — especially those who develop serious health conditions, need specialist care, or travel frequently — Medicare Advantage turns out to be one of the most expensive decisions they ever make.

This guide explains the real difference between these two paths, when each one makes sense, and what Medicare won’t tell you in the glossy brochures.

First, Understand How Medicare Actually Works

Original Medicare (Parts A and B) pays about 80% of most covered medical costs. The remaining 20% has no cap — meaning a serious illness or hospitalization could cost you tens of thousands of dollars out of pocket.

That 20% gap is the problem both Medigap and Medicare Advantage are trying to solve. They just solve it in very different ways.

Path 1: Medicare Supplement (Medigap)

A Medigap plan works alongside Original Medicare. You keep Medicare as your primary insurance, and the Medigap policy covers most or all of the leftover costs.

How it works:

You pay a monthly premium (typically $100–$350/month depending on age, gender, and location)
You can see any doctor or specialist in the country who accepts Medicare — no network, no referrals required
Most plans (especially Plan G, the most popular) cover the 20% Medicare doesn’t pay, your hospital deductible, and foreign travel emergency coverage
There are no prior authorizations for Medicare-covered services
You can get care at any hospital in America, including Mayo Clinic, Cleveland Clinic, or MD Anderson

The key trade-off: Higher monthly premiums, but far more predictable out-of-pocket costs.

Path 2: Medicare Advantage (Part C)

Medicare Advantage plans are offered by private insurance companies contracted with Medicare. The government pays the insurer a fixed monthly amount to cover your Medicare benefits.

How it works:

Many plans have $0 monthly premiums (very appealing on paper)
They typically include extras: dental, vision, hearing, gym memberships
You get care through a network of providers
You pay copays, coinsurance, and cost-sharing amounts when you use services
Plans have an annual out-of-pocket maximum (often $5,000–$8,500 or higher in-network, up to $13,300 out-of-network)
Plans can require prior authorizations before approving treatments, procedures, or specialist visits

The 4 Biggest Myths About Medicare Advantage

Myth #1: “$0 Premium Means $0 Cost”

The $0 premium is real — but it’s not the full story. When you actually use your Medicare Advantage plan for anything significant, the costs add up fast.

A hip replacement under a $0 Medicare Advantage plan might look like this:

Hospital copay: $350–$500/day for days 1–5
Surgeon fee: $800–$1,500 copay
Anesthesiologist: $200–$400 copay
Physical therapy: $40–$60 per visit × 20 visits = $800–$1,200
Total: $3,000–$6,000+ out of pocket

Under a Medigap Plan G, most of those costs after the Part B deductible ($257 in 2025) are covered by the supplement. You’d pay the deductible — and that’s it.

Myth #2: “My Doctors Are In-Network”

They are today. But networks change every year. Your primary care doctor or specialist may be in-network in January and out-of-network in February. If you’re in the middle of treatment for cancer, heart disease, or another serious condition when your doctor leaves the network, your options are limited:

Switch to a different in-network provider (disrupting continuity of care)
Pay out-of-network rates (often catastrophically expensive)
Wait for the next Annual Enrollment Period (October 15–December 7) to switch plans

Myth #3: “Prior Authorization Is Just a Formality”

Prior authorization is a formal approval process that Medicare Advantage plans use before covering many treatments, procedures, specialist visits, and hospital stays. Federal data shows that Medicare Advantage plans deny prior authorization requests at a significantly higher rate than original Medicare denials — with some plans denying 10–30% of requests.

If your authorization is denied, you can appeal — but appeals take time. If you need urgent cancer treatment, a cardiac procedure, or spinal surgery, waiting weeks for an appeal isn’t just inconvenient. It can change outcomes.

Original Medicare + Medigap has no prior authorization requirements for any Medicare-covered service. If Medicare covers it, it’s covered — period.

Myth #4: “I Can Switch Back to Medigap Anytime”

This is the myth that causes the most financial harm.

When you first enroll in Medicare at 65, you have a 6-month Medigap Open Enrollment Window. During this window, insurance companies must accept you at standard rates — regardless of any pre-existing conditions.

After that window closes, insurance companies in most states can use medical underwriting to accept or decline your application. If you’ve developed diabetes, heart disease, cancer, high blood pressure, or even had a joint replacement, you may be:

Declined for coverage
Offered coverage with a pre-existing condition waiting period
Charged significantly higher premiums

So if you start with Medicare Advantage, realize it’s not working for you after a health event, and then try to switch to a Medigap plan — you may find that no insurer will take you.

This is the trap. And it catches tens of thousands of seniors every year.

When Medicare Advantage Actually Makes Sense

Medicare Advantage isn’t wrong for everyone. Here are the situations where it genuinely is the better choice:

✓ You’re in excellent health and on few medications. If you rarely use your insurance, the $0 premium and included extras can provide real value. You may pay very little in a given year.

✓ You live in a stable local area. If you’re not going to seek specialized care outside your metropolitan area, and your doctors have a history of staying in the plan’s network, network restrictions matter less.

✓ You have limited income. Some Medicare Advantage plans include Part D (drug coverage) and offer low copays for routine care. For someone on a very tight fixed income, the lower monthly cost may be necessary even with the trade-offs.

✓ You want the extras. Dental, vision, hearing, and gym memberships can have real value if you use them consistently. For generally healthy seniors, these benefits can partially offset medical costs.

✓ Your area has plans with low out-of-pocket maximums. Not all Advantage plans are equal. In some areas, highly competitive plans have in-network out-of-pocket maximums of $2,000–$3,500 — making them more reasonable for cost-conscious, healthy seniors.

When Medigap Is Almost Always Better

✓ You have existing or chronic health conditions. If you’re managing heart disease, diabetes, cancer, kidney disease, COPD, or any other ongoing condition, the predictability of a Medigap plan is invaluable. The 20% Medicare doesn’t cover can add up to tens of thousands of dollars with serious illness — and Medigap eliminates most of it.

✓ You travel frequently or split time between states. Medicare Advantage plans are local — their networks don’t follow you. Medigap works everywhere Medicare is accepted, nationwide. If you winter in Arizona and summer in Oregon, Medigap is almost always the right call.

✓ You want access to any specialist. Mayo Clinic, Johns Hopkins, MD Anderson, Cleveland Clinic — the best specialty hospitals in America take Medicare. They may not take your specific Medicare Advantage plan. With Medigap, you go wherever you need to go.

✓ You want no surprises. Many people approaching retirement have spent their careers dealing with unpredictable costs. One of the greatest values of a Medigap plan is that your costs are predictable. You know your monthly premium. You know your deductible. Beyond that, the plan covers the rest.

✓ You want to protect a spouse or assets. A serious illness under Medicare Advantage can generate tens of thousands of dollars in out-of-pocket costs. That money comes from somewhere — savings, investments, or assets you intended to leave to a spouse or children.

The Numbers Side-by-Side

Here’s how the two paths can compare over time for someone who develops a serious health condition at age 70:

	Medigap Plan G	$0 Medicare Advantage
Monthly premium	$180/month	$0/month
5-year premium cost	$10,800	$0
Cancer treatment OOP (1 year)	~$257 (deductible only)	$5,000–$8,500 (OOP max)
Access to MD Anderson	✅ Yes	❌ May not be in network
Prior authorization required	❌ No	✅ Yes, for many procedures
Network restrictions	None	Yes (in-network required)
5-year total cost (with illness)	~$11,000–$12,000	$5,000–$42,500+

The premium savings evaporate quickly — and can reverse dramatically — the moment a significant health event occurs.

What About Plan F, Plan G, and Plan N?

If you go the Medigap route, the plan letter matters. Here’s a quick breakdown of the most popular options:

Plan G (Most Popular for New Enrollees) Covers everything Plan F covered except the Part B deductible ($257 in 2025). With Plan G, your only annual out-of-pocket expense for Medicare-covered services is that deductible. Everything else — the 20%, hospital costs, skilled nursing coinsurance, foreign travel emergencies — is covered.

Plan N Covers the same catastrophic costs as Plan G but with small copays ($20 for office visits, $50 for ER visits). Premiums are typically $30–$60/month lower than Plan G. A good option for healthy seniors who want to save on premiums and don’t mind the small copays.

Plan F (Grandfathered) Covers everything including the Part B deductible — but it’s only available to those who turned 65 before January 1, 2020. If you’re eligible, it’s the most comprehensive coverage available.

The Decision Framework: 5 Questions to Ask Yourself

Before choosing, ask yourself these five questions honestly:

Am I currently managing any health conditions? If yes, lean strongly toward Medigap.
Do I have doctors or specialists I want to keep seeing? If yes, verify they accept Medigap (they accept Medicare), not just your specific Advantage plan.
Do I travel more than 2–3 months per year outside my home area? If yes, Medigap gives you national coverage.
Could I absorb a $5,000–$8,500 unexpected medical expense without significant financial stress? If no, the out-of-pocket maximum on Advantage plans may be too risky.
Am I currently in my 6-month Medigap Open Enrollment Window? If yes, you have the guaranteed right to enroll at standard rates. That window doesn’t come back.

One More Thing: The Importance of Independent Advice

Insurance companies that sell Medicare Advantage have a financial incentive to enroll you — they receive a fixed monthly payment from the government for each person enrolled, regardless of how much care you use.

A captive agent (one who works for a single insurance company) can only show you their company’s plans. An independent Medicare advisor — one who works with multiple carriers — can compare both Advantage and Medigap options across all available carriers and find the combination that actually fits your health situation, budget, and lifestyle.

At Legacy Wealth Services, Rodney Cummings works independently across a wide portfolio of carriers. He’s not paid more to recommend Advantage over Medigap, or vice versa. His only job is to find the right plan for you.

Next Steps

If you’re approaching Medicare eligibility, or if you’re already on Medicare and wondering whether you’re on the right plan, the best first step is a no-pressure conversation with an independent advisor.

📞 Medicare Questions & Plan Comparison: (503) 843-8349 (This line is recorded for compliance purposes)

📅 Schedule a Free Medicare Review: Book a 30-Minute Appointment

📍 Serving clients in 26 states including Oregon, Washington, California, Texas, Florida, and more.

Rodney Cummings is an RSSA® (Registered Social Security Analyst) and independent insurance professional licensed in 26 states. He specializes in Medicare planning, retirement income strategies, and integrated wealth protection for pre-retirees and retirees.

This article is for educational purposes only and does not constitute personalized insurance or financial advice. Medicare plan availability and costs vary by location and are subject to change.

Medicare Advantage vs. Medigap Supplement: The Decision Most Oregon Seniors Get Wrong