Pat Herrington is sixty-six years old and lives in Oshkosh, Wisconsin, which puts her in a county with fourteen Medicare Advantage plans to choose from. That sounds like abundance. It isn’t.

Pat called me in February, three months after switching from her Medicare Supplement policy to a Medicare Advantage plan during last fall’s open enrollment. The reason she switched was the premium. Her Plan G supplement was running $218 a month. The Advantage plan was $0 a month. She did the math on $218 times twelve, came up with $2,616, and moved.

Now Pat needs a total knee replacement. Her orthopedic surgeon is out of network. The hospital she’s used for twenty years is in network, but the anesthesiology group that works there isn’t. The Advantage plan denied her initial pre-surgery consultation referral, which added six weeks to the timeline while she filed an appeal.

The $0 premium has cost her more than the $218 premium ever did. And here’s the part that matters most: Pat can’t go back. She’d sign up for her old Plan G tomorrow. But at sixty-six, with a knee that needs replacing, she’s subject to medical underwriting. The insurer’s answer isn’t going to be yes.

I’ve told versions of this story too many times. The Medicare coverage decision you make at sixty-five isn’t easily reversible. Most people don’t know this. The industry, for obvious reasons, doesn’t lead with it.

Here’s the honest comparison.

What You’re Actually Comparing

Let’s start with what each product actually is, because the marketing has muddied this considerably.

Original Medicare is two parts. Part A covers hospitalization, skilled nursing facility care after a qualifying hospital stay, some home health services, and hospice. Part B covers outpatient care: doctor visits, lab work, preventive services, durable medical equipment, and some outpatient drugs. Most people don’t pay a premium for Part A if they or their spouse worked at least ten years. Part B costs $202.90 a month in 2026.

Here’s what nobody explains at the free dinner seminar: Original Medicare has no annual out-of-pocket maximum. None. The Part A deductible is $1,736 per benefit period in 2026, and “per benefit period” matters because you can trigger multiple benefit periods in a single year if you’re hospitalized, discharged, and hospitalized again. Part B has a $283 annual deductible, after which you typically pay 20% of covered services with no ceiling. A bad year, a run of hospitalizations, a complex outpatient course of treatment, and your out-of-pocket cost could reach five or six figures. That’s the actual design of the program.

A Medicare Supplement policy, also called Medigap, fills those holes. That’s the entire job description. You still have Original Medicare underneath. You see any physician or hospital that accepts Medicare anywhere in the country, with no referrals and no prior approvals required. Medicare pays its share, and the Supplement picks up what’s left. The most popular option for new enrollees right now is Plan G, which covers essentially everything except that $283 Part B deductible. After that single annual payment, you’re fully covered. No networks, no surprise bills, no arithmetic at the end of a hospital stay.

Medicare Advantage, called Part C, is something different. It replaces Original Medicare entirely. You hand your coverage over to a private insurer that contracts with Medicare to provide your Part A and Part B benefits, usually bundled with Part D prescription drug coverage. The plan imposes its own provider network, its own prior authorization requirements, and its own cost-sharing structure. Average monthly premium in 2026 is $14 nationwide, according to CMS data, and many plans charge $0.

The Real Cost of Free

When people see a $0 premium, they tend to think they’ve found a deal. What they’ve actually done is swap a monthly premium for a different cost structure, and that swap isn’t always in their favor.

With Advantage, you pay copays per service. A primary care visit might run $10, a specialist $40, a hospital stay a daily copay for the first several days. The copays accumulate. The in-network out-of-pocket maximum for an Advantage plan is $9,250 in 2026. Out-of-network, the cap is $13,900. Those limits exist to protect you from catastrophic costs, and that protection is real. But the cap only works when you’re using in-network providers, and Advantage networks vary enormously by geography and plan.

In a large metro area, a broad-network Advantage plan may include most of the physicians you’ve been seeing for years. In smaller cities or rural counties, the network can be thin. Plans can change their provider lists annually. A hospital that’s in network when you enroll may not be in network eighteen months later.

Prior authorization is the other piece that doesn’t appear in the summary of benefits. Before an Advantage plan will approve a specialist visit, a procedure, or sometimes a test, you may need advance approval. A 2022 report from the HHS Office of Inspector General reviewed a sample of Advantage plan denials and found that 13% of denied prior authorization requests actually met Medicare’s own coverage criteria, meaning those services should have been covered. Most requests are approved. But when they’re delayed or denied, you’re filing appeals while managing a health problem.

Advantage isn’t a bad product. It’s a product, with incentives and cost structures that are different from what the $0 premium suggests.

When Advantage Actually Makes Sense

There are real situations where Advantage is a reasonable choice, and I want to be fair about this.

Healthy, low utilization, no existing specialist relationships you’d be reluctant to leave. A $0-premium plan with $10 copays will probably cost you less over a year than a $220-a-month Supplement. At low utilization, the premium savings compound into real money.

The bundled dental, vision, and hearing benefits also deserve honest consideration. Original Medicare covers none of these, which is one of the more cynical gaps in a program designed for the population most likely to need them. A hearing aid costs upward of $3,000 out of pocket. A dental implant can run $4,000 to $6,000. Many Advantage plans bundle some coverage for these into the premium. It’s rarely comprehensive, but for someone who wears glasses and goes to the dentist regularly, that bundled value is real money and it doesn’t show up in a simple premium comparison.

A third situation: if you live near a high-quality integrated health system that participates in Medicare Advantage and coordinates care well. Some of the large HMO-style systems do this effectively. If you’re willing to receive all your care within that system, you may get better-organized care than you’d piece together independently under Original Medicare. This is market-specific, and worth researching in your area before assuming it applies to you.

When Supplement Makes More Sense

Existing chronic conditions change the calculus significantly. Diabetes. Heart disease. Arthritis that’s heading toward surgery. Any condition that means ongoing specialist visits, procedures, or the real possibility of hospitalization. Network restrictions and prior authorization are manageable friction when you’re healthy. They become genuine obstacles when you have time-sensitive health needs and a relationship with a specific specialist you’ve been seeing for three years.

Travel matters too. Three months in Arizona, nine months in Wisconsin, or any significant time spent outside your plan’s service area. A Medicare Supplement covers you anywhere Medicare is accepted. Most Advantage plans cover only emergency care when you’re out of their service area. Urgent care is not emergency care. If you travel, read the out-of-area coverage section carefully before committing.

The broader point is predictability. A Medicare Supplement covers you with any physician or hospital that accepts Medicare, without referrals, without prior approvals, without wondering whether today’s provider is in network. For someone managing an ongoing condition with established specialists, that reliability has dollar value that doesn’t appear in a premium comparison.

Plan G runs around $220 a month at age sixty-five on average, though rates vary substantially by state, insurer, and whether premiums are community-rated or age-rated. That’s $2,640 a year. Over a decade, adjusting for annual increases, it’s a real number. I’m not dismissing it. But the Plan G premium buys you something concrete: access and predictability. Whether that trade is worth it depends on your health, your providers, and your genuine tolerance for the network-and-authorization process.

The Trap Nobody Explains Until It’s Too Late

When you turn sixty-five and enroll in Medicare Part B, you have a six-month Medigap open enrollment window. During those six months, insurers are legally required to sell you any Medigap plan at standard rates, regardless of your health history. Pre-existing conditions don’t matter. You cannot be denied. You cannot be charged extra.

After those six months, the protection disappears. Outside the guaranteed issue window, Medigap insurers can use medical underwriting. They can deny your application. They can charge higher rates. A sixty-seven-year-old with controlled hypertension, a prior joint replacement, or managed type 2 diabetes may find Plan G unavailable or priced significantly above the standard rate.

This matters for the Advantage question because of something called the Trial Right. If you enroll in Medicare Advantage when you first become eligible for Medicare and decide within twelve months that you want to return to Original Medicare with a Supplement, you retain your guaranteed issue rights. After that twelve months, you’re in the underwriting pool. You can still apply for a Medigap policy. Approval is just no longer guaranteed.

A handful of states provide additional protections. Minnesota is implementing annual guaranteed issue rights for beneficiaries between sixty-five and seventy, starting later in 2026. Delaware has a birthday rule allowing plan changes around your birthday each year. But in most of the country, federal rules apply, and federal rules put the burden on you to enroll correctly at the start.

Pat Herrington isn’t a cautionary tale about Advantage being a defective product. She’s a cautionary tale about making a reversible-seeming decision without knowing its time limit.

The Enrollment Calendar Worth Knowing

The Annual Enrollment Period runs October 15 through December 7. During this window you can join, switch, or drop a Medicare Advantage plan, switch between Original Medicare and Advantage, or change your Part D drug plan. Changes take effect January 1.

The Medicare Advantage Open Enrollment Period runs January 1 through March 31. If you’re already enrolled in an Advantage plan, you can switch to a different plan or return to Original Medicare and add a standalone Part D plan. This window doesn’t grant guaranteed issue rights for Medigap unless you qualify independently.

Your initial enrollment window is seven months: three months before your 65th birthday month, the birthday month itself, and three months after. If you’re still covered under an employer plan at a company with twenty or more employees, you can delay Medicare enrollment without penalty. The rules for employer-based coverage are specific and worth verifying, because the Part B late enrollment penalty is 10% per twelve months you were eligible but didn’t enroll, and it’s permanent.

The Honest Summary

If you’re healthy, your utilization is low, your budget matters, and you don’t have strong existing provider relationships that might fall outside a network, Advantage deserves a real look, particularly if you’re in a market with strong plan options or a bundled dental and hearing benefit you’d otherwise pay out of pocket.

If you have chronic conditions, existing specialist relationships, a plan to travel significantly, or the kind of temperament that finds prior authorization stressful, buy your Plan G during your initial enrollment window, while you have guaranteed acceptance, and be done with it.

Either way, understand what you’re choosing before October 15. The $0 premium isn’t free coverage. Something pays for the marketing, the agent commissions, and the insurer’s margin. That something is a combination of the Medicare capitation payment the plan receives on your behalf and the cost management built into the network and authorization process. That’s not a condemnation. It’s a description. Knowing the description helps you choose.

I’ve written about the healthcare gap between early retirement and Medicare eligibility and why the Medicare start date is often the single biggest financial constraint on when people can leave work. And if you’re thinking about the full arc of healthcare costs in retirement, my piece on the long-term care conversation most families aren’t having covers a category of cost that neither Advantage nor Supplement touches.

The Medicare choice isn’t technically complicated. It’s consequential. It’s worth an hour of research before October 15 rather than a decision made at a free steak dinner.

The information exists. Go find it.