Original Medicare covers hospital stays, doctor visits, and outpatient care, but it does something no Medicare Advantage plan is allowed to do: it lets the bills run without any annual ceiling. Parts A and B keep charging deductibles and a flat 20 percent coinsurance no matter how high a year’s total climbs, so a single serious illness can push a beneficiary’s share into five figures. Every Medicare Advantage plan, by contrast, must stop charging once in-network costs reach a federal limit, set at $9,250 for 2026. That gap is one of the most consequential differences in the program, and it is invisible until the year a bill turns catastrophic.
The 20 percent that never stops under Part B
Under Part B, after a beneficiary meets the annual deductible, the standard cost-sharing is 20 percent of the Medicare-approved amount for physician services, outpatient care, durable medical equipment, and drugs administered in a clinic. Nothing in the year converts that share to zero. For a routine office visit the math is modest, but for a cancer regimen, a long course of infusions, or repeated outpatient procedures, an open-ended 20 percent quickly becomes the number that decides the household budget.
Part A layers on its own exposure. The inpatient hospital deductible is charged per benefit period rather than per calendar year, so a beneficiary who is admitted, discharged, and then readmitted after a new benefit period begins can owe the full deductible more than once in the same twelve months, according to Medicare’s published cost rules. Long stays add daily coinsurance charges once an admission passes 60 days. None of it counts toward a cap, because no cap exists on the medical side.
Prescription drugs sit under a separate structure that does have a ceiling. Part D caps a beneficiary’s yearly out-of-pocket drug spending at $2,100 for 2026, a genuine limit after which covered medications cost nothing more. But that cap applies only to drugs, not to the Part A and Part B charges that make up most of a serious illness. Reaching the drug ceiling does nothing to slow the coinsurance clock on a hospitalization or a specialist’s bill.
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How Medicare Advantage caps the damage
A Medicare Advantage plan replaces that open-ended design with a hard stop. For 2026 the federal maximum on in-network out-of-pocket costs is $9,250, down slightly from $9,350 the year before, and plans that also cover out-of-network care carry a combined limit of $13,900, a structure spelled out across the Medicare Advantage plan rules. Once a member reaches the number, the plan pays 100 percent of covered medical costs for the rest of the year.
The cap is not free money. Advantage plans achieve it through provider networks, prior authorization, and referral requirements that Original Medicare does not impose, and the protection applies only to care delivered inside the network. Step outside it, or run into a coverage denial, and a member’s exposure widens again. The tradeoff is a firm dollar ceiling in exchange for tighter rules on where and how care is delivered, not a clean upgrade over Original Medicare.
That tradeoff is exactly why the annual coverage-choice window carries weight. From October 15 to December 7 a beneficiary can move between Original Medicare and an Advantage plan for the following year, and the medical outlook — a scheduled surgery, a chronic condition, a cancer history — is what should tip the decision. A healthy year favors flexibility; a high-cost year favors the cap.
Medigap fills the ceiling Original Medicare leaves out
The tool built to close the gap is a Medigap policy, sold by private insurers to sit alongside Original Medicare. Depending on the plan letter, Medigap covers some or all of the Part A and Part B cost-sharing that would otherwise run without limit — the 20 percent coinsurance, the hospital deductibles, and the daily charges on extended stays. In effect it manufactures the out-of-pocket ceiling the program itself declines to build in.
The catch is timing. The strongest guaranteed right to buy a Medigap policy without medical underwriting runs during the six months after a beneficiary first enrolls in Part B at 65. Miss that window and, in most states, an insurer may screen for health conditions and charge more or refuse coverage outright. The result is that the people who most need the cap, those already diagnosed with something expensive, are often the ones who can no longer buy the protection at an affordable price.
The upshot is a quiet fork in the road most enrollees pass without noticing. Original Medicare offers the widest choice of doctors and no network, but hands the beneficiary unlimited financial exposure unless it is paired with Medigap. Medicare Advantage caps the exposure but fences the care. The one arrangement that does not exist is Original Medicare, standing alone, with a built-in ceiling — and assuming otherwise is how an ordinary year of treatment turns into a bill with no top.
This article was produced with AI assistance and reviewed against primary sources by The Money Overview editorial team.
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