A 66-year-old comparing plans on Medicare.gov sees two boxes side by side. The first is a Medicare Advantage plan with a $0 monthly premium and a $9,250 in-network out-of-pocket maximum. The second is Original Medicare plus a Medigap Plan G supplement, with a separate monthly premium on top of Part B. She is healthy, takes one generic drug, and has not been hospitalized in a decade. The zero-premium plan looks obvious until the year it does not.
The choice matters most for people approaching their first Medicare decision, or for those already in Medicare Advantage who are wondering whether a switch back to Original Medicare is realistic. Employer coverage after 65 can change the timing and cost analysis, so that situation needs its own review.
The Two Bills You Actually Pay
Both routes generally start with the same fixed Part B cost. In 2026, the standard Part B premium is $202.90 a month, and the Part B annual deductible is $283. Some beneficiaries pay more because of IRMAA, and some receive help with premiums, but Part B is the base cost behind both choices.
A Medigap Plan G premium depends on state, age, insurer, and rating method. Add a standalone Part D drug plan, and the Original Medicare route often has a higher monthly premium before any care. Medicare Advantage can cost $0 in premium above Part B and often bundles drug coverage.
In a healthy year, Advantage can cost less in premiums, sometimes by thousands of dollars. That price gap is one reason Medicare Advantage has grown so quickly: in 2026, 55% of eligible Medicare beneficiaries are enrolled in Medicare Advantage.
What the $9,250 Cap Does Not Cover
The advertised protection on Advantage is the in-network maximum for covered Part A and Part B services. In 2026, the federal cap is $9,250 for in-network services and $13,900 for combined in- and out-of-network services on plans that cover out-of-network care. The average in-network limit across plans is $5,421.
Two things can sit outside that cap. First, Part D prescription spending has its own separate structure. Second, out-of-network care on an HMO is generally not covered except for emergencies and limited situations, while a PPO may apply those costs to the higher combined ceiling. A specialist your plan does not contract with, or a surgeon your oncologist prefers, may fall outside the number printed on the brochure.
Original Medicare plus Plan G works differently. After the $283 Part B deductible, Plan G generally pays the Part B coinsurance Medicare leaves behind for Medicare-covered services. You can use any doctor or hospital that accepts Medicare, anywhere in the country. In a bad year, the Plan G holder’s medical cost-sharing for covered services is often close to that deductible plus twelve months of premiums.
The Bad Year, Priced Out
Picture a cancer diagnosis at 72. Chemotherapy, imaging, hospital admissions. On an Advantage plan with the federal ceiling, the enrollee can owe up to $9,250 for covered in-network medical care, plus Part D cost-sharing. If the best specialist is out of network on a PPO, covered medical exposure can climb toward the $13,900 combined ceiling. On an HMO, nonemergency out-of-network care may not be covered at all.
On Original Medicare plus Plan G, the same year may cost roughly $283 in Part B medical cost-sharing for Medicare-covered services, on top of Medigap, Part B, and Part D premiums. A single bad year can erase several years of premium savings while also testing network access at the worst possible moment.
The Trap That Makes the First Choice Nearly Permanent
Moving from Original Medicare to a Medicare Advantage plan is often straightforward during the right enrollment period. Moving back later can be harder. Outside the initial six-month Medigap open enrollment window that begins when you are 65 or older and enrolled in Part B, most states let Medigap insurers medically underwrite. A cancer history, heart condition, or diabetes can produce a denial or a higher premium. Connecticut, Massachusetts, Maine, and New York have broader protections; most states do not.
The Advantage plan you choose at 65 may be less reversible than it feels. The healthy 66-year-old picking the zero-premium plan is also shaping what her Medigap options may look like at 76, when her health and underwriting profile could be very different.
What To Do
- If you are inside your six-month Medigap open enrollment window, price Plan G and Plan N before it closes. That window is one-time under federal law and does not repeat every year.
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If you are choosing Advantage, pull the plan’s Summary of Benefits and check the in-network out-of-pocket maximum, referral rules, prior authorization rules, and out-of-network coverage. Confirm that your primary care doctor, preferred hospital system, and any specialist you already see are in network.
- Check your state’s Medigap rules. If you live in a state with broader guaranteed-issue protections, the switch-back trap may be smaller, but the details still matter because protections, plan choices, and timing differ by state.
Choose for the Sick Year, Not Just the Cheap Year
The zero-premium Advantage plan can be the rational choice for a healthy retiree who understands the network, the out-of-pocket maximum, and the risk of future Medigap underwriting. The mistake is treating the premium as the whole price. Medicare planning should ask what happens in the year care gets expensive, when switching may be harder and access matters more than the monthly bill.
Figures reflect 2026 Medicare rules published by CMS in November 2025. Verify current numbers at Medicare.gov before making an enrollment decision.
Contact [email protected] for any questions or corrections.
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