A 68-year-old retiree in Ohio picked a $0-premium Medicare Advantage HMO at age 65. Three years later, a shoulder tear sent her to the region’s best rotator-cuff surgeon. He was out of network. Her plan’s answer: pick someone on the list or pay for the preferred surgeon herself. That is the trap that can turn a “free” plan into expensive coverage at the exact moment a retiree wants more choice.
Original Medicare with Medigap works differently because beneficiaries can use any doctor or hospital in the U.S. that accepts Medicare, and the supplement helps pay Medicare cost-sharing. The network problem is most urgent for people in Medicare Advantage, especially those choosing a plan for the first time or considering an HMO with a narrow local network.
The out-of-network cliff most enrollees never test
Medicare Advantage plans advertise an out-of-pocket maximum, but the number that hurts may be outside the main brochure headline. In 2026, federal rules cap in-network out-of-pocket spending at $9,250 for covered Part A and Part B services. For plans that cover out-of-network care, the combined in-network and out-of-network cap is $13,900. HMOs generally require network providers for routine care, with exceptions such as emergency care, urgent care, and out-of-area dialysis.
Run the sick-year math against Original Medicare. A beneficiary on Original Medicare pays the $202.90 Part B premium and a $283 annual Part B deductible in 2026. Add a Medigap Plan G premium, which varies by state, age, insurer, and rating method, and the remaining medical cost-sharing for Medicare-covered services is usually close to the Part B deductible. Any surgeon in the country who accepts Medicare is available without a plan network.
The HMO retiree who wants a specific non-network surgeon often has three practical options: use an in-network surgeon, ask the plan whether any exception or referral path exists, or pay out of pocket for noncovered care. Waiting for the next enrollment period may help future coverage, but it may not solve a surgery decision that needs to happen now.
The switch back is the second trap
Moving from Original Medicare to a Medicare Advantage plan at age 65 can feel reversible. In many states, it is only partly reversible. After the one-time six-month Medigap open enrollment window that starts when someone is 65 or older and enrolled in Part B, most states let Medigap insurers medically underwrite applicants. A retiree with a new diagnosis or cardiac history can be denied or charged more. Connecticut, New York, Massachusetts, and Maine offer broader guaranteed-issue protections, though the rules differ by state.
That can turn the initial Advantage decision into something close to a one-way door. The cost of getting out is not just the next premium. It is the risk that a Medigap insurer may not sell an affordable policy after health has changed.
The break-even in dollars
In a healthy year, the Advantage HMO can win by a wide margin. A $0 plan premium beats a separate Medigap premium, and the savings can add up over several healthy years. The exact spread depends on the local Medigap quote, the Part D plan, and the Advantage plan’s copays.
In a bad year, the ledger can flip. Hit the in-network cap on an Advantage plan and the enrollee can spend up to $9,250 for covered Part A and Part B services. On a PPO, covered out-of-network care can push exposure toward the $13,900 combined ceiling. On an HMO, routine out-of-network care may not be covered at all. Original Medicare plus Plan G generally leaves the beneficiary with the annual premium plus the $283 Part B deductible for Medicare-covered services.
The pressure on this math is not easing. The 2026 Social Security COLA is 2.8%, and average annual spending reached $78,535 per consumer unit in 2024, according to the BLS Consumer Expenditure Survey. A five-figure uncovered medical bill can overwhelm a retiree budget even when the monthly plan premium looks manageable.
What to do
Three actions, in order of urgency:
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Start with the Medigap clock. If you are choosing coverage for the first time and can afford the premium, price Original Medicare with Plan G and Plan N during your six-month Medigap open enrollment window. That is the main federal window when underwriting cannot block you.
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Check the network before you need surgery. If you are already on a Medicare Advantage HMO, call the plan and confirm the in-network hospitals, surgeons, and specialists you would actually use. If a key provider is missing, use the October 15 to December 7 Annual Enrollment Period to compare another Advantage plan, a PPO, or Original Medicare.
- Do not drop Advantage first and shop Medigap later. Before switching back to Original Medicare, apply for Medigap and get the underwriting answer in writing unless you have a guaranteed-issue right. Otherwise, you could leave a capped Advantage plan and end up on Original Medicare without a supplement or annual out-of-pocket limit.
Choose the Network Before the Diagnosis
A $0 premium can be a reasonable trade-off when the doctors, hospitals, referral rules, and out-of-pocket limits fit the retiree’s health needs. The mistake is treating the premium as the whole price. Medicare Advantage is a network decision first and a premium decision second, because the provider you want most may matter only after switching becomes hard.
Sources: 2026 Part B premium and deductible figures come from the CMS “2026 Medicare Parts A & B Premiums and Deductibles” fact sheet. Medicare Advantage out-of-pocket maximums and Part D exclusion come from KFF’s 2026 Medicare Advantage analysis. HMO network rules, Medigap open enrollment, Original Medicare provider access, and Medigap benefit details come from Medicare.gov. Social Security COLA data come from SSA, and spending data come from the BLS Consumer Expenditure Survey.
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