Original Medicare covers a large share of hospital and medical costs, but it was never built with a ceiling on what a beneficiary pays out of pocket in a bad year. Medicare’s own cost guidance states plainly that there’s no yearly limit on what a person pays out of pocket under Original Medicare unless they also carry supplemental coverage such as a Medicare Supplement Insurance policy or enroll in a Medicare Advantage plan instead — a structural gap, not an oversight, that has shaped an entire private insurance industry around filling it.
The math behind an open-ended bill
The exposure comes from how Part A and Part B split costs rather than capping them. Part B generally leaves a beneficiary responsible for 20 percent coinsurance on most covered services after a $283 annual deductible in 2026, and that 20 percent applies to every qualifying service for the rest of the year with no dollar ceiling — someone who needs extensive outpatient treatment or a series of specialist procedures keeps paying that percentage on every claim, no matter how high the cumulative total climbs, on top of the $202.90 monthly Part B premium owed regardless of how many services get used.
Part A adds its own separate exposure for a long hospitalization: a beneficiary pays a $1,736 deductible per benefit period in 2026, then $434 a day for days 61 through 90, and $868 a day while drawing on a lifetime bank of 60 reserve days beyond that — after which Medicare’s own cost chart says the patient pays all costs. There’s no limit to the number of benefit periods a person can have in a year, so a second, unrelated hospitalization can trigger the deductible again.
Skilled nursing care adds a third layer of exposure that runs on its own separate schedule. The same cost chart shows the first 20 days of a covered skilled nursing facility stay at $0, but days 21 through 100 cost $217 a day in 2026, and Medicare states plainly that past day 100, the patient pays all costs. That ceiling applies independently of the hospital deductible and the Part B coinsurance described above, so a beneficiary who is hospitalized and then needs extended nursing care afterward can face all three forms of exposure stacking in the same benefit period.
Durable medical equipment costs compound the same exposure rather than escaping it: Medicare’s chart lists a 20 percent coinsurance on items like wheelchairs, walkers, and hospital beds with no dollar cap either, layering onto whatever coinsurance a beneficiary already owes for the underlying care that equipment supports.
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Why Medicare Advantage looks different on paper
Medicare Advantage plans, the private alternative to Original Medicare, work under a different rule: each plan sets its own out-of-pocket limit that the government caps. For 2026, that federal ceiling sits at $9,250 for in-network services and $13,900 when out-of-network care is combined in — once a beneficiary hits their plan’s limit, the plan pays 100 percent of covered services for the rest of the calendar year.
That structural difference is a real tradeoff, not simply an upgrade. Medicare Advantage plans typically use provider networks and prior authorization requirements that Original Medicare doesn’t impose, so the dollar protection of an out-of-pocket cap comes bundled with restrictions on which doctors and hospitals a beneficiary can use without paying more or being denied coverage outright.
How Medigap fills the specific hole instead
A Medigap policy takes a different approach than an out-of-pocket cap: rather than setting its own ceiling, it pays some or all of the cost-sharing Original Medicare leaves behind — the Part A and Part B deductibles, the 20 percent Part B coinsurance, and other gaps, depending on which of the ten standardized lettered plans a person buys. A comprehensive letter plan can functionally erase the open-ended exposure described above without ever needing a stated dollar limit of its own.
Buying a Medigap policy doesn’t replace Original Medicare or its premiums, either. A beneficiary must keep paying the Part B premium every month to keep the Medigap policy in force, since Medigap is designed to work alongside Original Medicare rather than instead of it — the policy fills the cost-sharing gap, it doesn’t substitute for the underlying coverage.
That’s also why a Medigap policy is priced and sold entirely separately from Medicare itself, varying by which policy, where the buyer lives, and which insurance company sells it — and why the guaranteed right to buy one without a health question is concentrated into the narrow window that opens when someone first enrolls in Part B at 65 or older, since insurers underwrite Medigap applications more freely once that window closes.
The absence of a built-in ceiling in Original Medicare isn’t a modern gap so much as a design choice baked into the program from the start, and it’s the single biggest reason a private supplemental insurance market exists alongside a government program that already covers most beneficiaries’ routine care. Choosing between a Medigap premium and simply accepting the open-ended 20 percent exposure is, in practical terms, a bet on how much unpredictable, high-cost care someone expects to need in years they can’t yet see coming.
This article was researched and drafted with the assistance of artificial intelligence.
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