If you've ever received a hospital bill and wondered why Medicare didn't cover everything, you're not alone. Original Medicare — the federal program consisting of Part A and Part B — pays a substantial share of inpatient hospital costs, but it does not pay everything. Understanding exactly what Medicare covers, what you'll owe, and when your coverage runs out is one of the most important things any Medicare beneficiary can know. In 2026, the numbers are significant enough that going into a hospital without understanding your exposure is a financial risk you shouldn't take.
Medicare Part A is the portion of Original Medicare that covers inpatient hospital care. When you're admitted to a hospital as an inpatient — meaning a doctor formally admits you with a written order — Part A kicks in. It covers your semi-private room, meals, general nursing care, drugs administered during your stay, and most other hospital services and supplies. What it does not cover is the full bill, and the gap between what Medicare pays and what you owe can be substantial depending on how long you stay.
The 2026 Medicare Part A inpatient deductible is $1,676 per benefit period. This is the single most important number to understand, and it trips up beneficiaries constantly because it does not work like a typical annual deductible. A benefit period begins the day you're admitted as an inpatient and ends when you've been out of the hospital — or a skilled nursing facility — for 60 consecutive days. If you're hospitalized in January, recover, go home, and then are re-admitted in April after 60 days have passed, you owe the $1,676 deductible again. There is no cap on how many benefit periods you can have in a year, which means a beneficiary with multiple hospitalizations could owe this deductible two, three, or even four times in a single calendar year.
Once you've paid the deductible, Medicare Part A covers 100% of your covered hospital costs for days 1 through 60 of your stay. This is the window where Medicare is most generous. For the vast majority of hospitalizations — which average around 4 to 5 days nationally — most beneficiaries won't owe anything beyond that initial deductible. But longer stays change the math dramatically. From day 61 through day 90, you pay a daily coinsurance of $419 per day in 2026. That means a 90-day hospital stay — not uncommon for a serious illness, major surgery recovery, or stroke rehabilitation — would cost you the $1,676 deductible plus $12,570 in daily coinsurance, for a total out-of-pocket exposure of $14,246 before Medicare stops covering the stay entirely.
Beyond day 90, Medicare gives you what it calls "lifetime reserve days" — a one-time bank of 60 additional days you can draw on across your entire lifetime. In 2026, each lifetime reserve day costs you $838 in daily coinsurance. Once those 60 days are exhausted, Medicare pays nothing for any additional inpatient days. This is the coverage cliff that can devastate beneficiaries who experience a catastrophic illness requiring extended hospitalization. A beneficiary who uses all 90 regular days plus all 60 lifetime reserve days would owe the $1,676 deductible plus $12,570 in coinsurance for days 61–90, plus $50,280 in lifetime reserve day coinsurance — a total of $64,526 in out-of-pocket costs before Medicare stops paying entirely.
Data Snapshot: According to CMS.gov data from the Medicare & Medicaid Statistical Supplement, Medicare Part A enrolled approximately 57 million beneficiaries as of 2024, and inpatient hospital services remain the single largest category of Part A spending. CMS data also shows that the average length of an inpatient hospital stay for Medicare beneficiaries is approximately 5.4 days — meaning most beneficiaries will only encounter the Part A deductible and not the daily coinsurance thresholds. However, beneficiaries with chronic conditions, cancer diagnoses, or major surgical procedures face meaningfully higher average lengths of stay, making the coinsurance structure a real financial risk for a significant subset of the Medicare population.
One critical distinction that catches many beneficiaries off guard is the difference between inpatient and observation status. If a hospital places you under "observation status" rather than formally admitting you as an inpatient, your stay is billed under Part B rather than Part A — even if you're sleeping in a hospital bed for multiple nights. This matters enormously because Part B covers outpatient services differently, and more importantly, a stay under observation status does not count toward the three-day inpatient hospital stay requirement that Medicare uses to qualify you for covered skilled nursing facility care afterward. If you're hospitalized and unsure of your status, you have the right to ask your care team directly. Hospitals are required under the NOTICE Act to provide written notification if you're under observation status for more than 24 hours.
Skilled nursing facility care is closely linked to Part A hospital coverage and deserves its own explanation. After a qualifying inpatient hospital stay of at least three days, Medicare Part A covers skilled nursing facility care for up to 100 days per benefit period. Days 1 through 20 are fully covered with no coinsurance. From day 21 through day 100, you pay $209.50 per day in 2026 coinsurance. After day 100, Medicare pays nothing for skilled nursing facility care. For beneficiaries recovering from a hip replacement, stroke, or cardiac event, this 100-day window — and the daily coinsurance starting at day 21 — is a major cost consideration that should factor into any discharge planning conversation.
So what can you do to protect yourself from these costs? There are two primary paths, and they are mutually exclusive — you generally cannot have both. The first is a Medicare Supplement Insurance plan, commonly called Medigap. These are standardized private insurance policies sold alongside Original Medicare that are designed specifically to fill the gaps in Part A and Part B coverage. Medigap Plan G, the most popular plan for new enrollees in 2026, covers the Part A deductible, all Part A coinsurance and hospital costs up to an additional 365 days after Medicare benefits are exhausted, and Part B coinsurance. In practical terms, Plan G means that after you pay the annual Part B deductible ($257 in 2026), your hospital bills are largely covered regardless of how long you stay. Average monthly premiums for Plan G vary significantly by age, location, and insurer — typically ranging from roughly $100 to $250 per month for a 65-year-old — but the financial protection for a serious hospitalization can be worth multiples of that annual premium cost.
The second path is Medicare Advantage, also called Part C. These are private insurance plans that replace Original Medicare entirely and must cover at least the same benefits as Part A and Part B. Most Medicare Advantage plans charge lower monthly premiums than Medigap — many have $0 premiums — but they use cost-sharing structures like copayments and coinsurance rather than the gap-filling approach of Medigap. For a hospital stay, a Medicare Advantage plan might charge a flat copayment per day for the first several days, then cover the rest. The trade-off is that Medicare Advantage plans use provider networks, may require prior authorization for hospital admissions, and have annual out-of-pocket maximums that in 2026 can be as high as $9,350 for in-network care. For beneficiaries who are generally healthy and want lower monthly costs, Medicare Advantage can be a reasonable choice. For those with complex conditions who want the freedom to see any Medicare-accepting provider without network restrictions, Medigap with Original Medicare often provides more predictable protection.
If you're currently enrolled in Original Medicare without any supplement coverage — sometimes called "bare" Medicare — you are exposed to the full cost-sharing structure described above. The good news is that you have options to change your coverage. The Annual Enrollment Period runs from October 15 through December 7 each year, during which you can switch between Original Medicare and Medicare Advantage, or change Medicare Advantage plans. The Open Enrollment Period from January 1 through March 31 allows Medicare Advantage enrollees to switch plans or return to Original Medicare. Returning to Original Medicare from Medicare Advantage and then purchasing a Medigap plan, however, may require medical underwriting in most states — meaning insurers can charge you more or deny coverage based on your health history. The best time to buy Medigap is during your initial six-month Medigap Open Enrollment Period, which begins the month you turn 65 and are enrolled in Part B, when you have guaranteed issue rights regardless of your health.
For beneficiaries who cannot afford Medigap premiums and don't want Medicare Advantage, there are assistance programs worth knowing about. The Medicare Savings Programs — administered through state Medicaid agencies — can help pay Part A and Part B premiums, deductibles, and coinsurance for beneficiaries with limited income and assets. Eligibility thresholds vary by state, but even beneficiaries with modest incomes above the poverty line may qualify for partial assistance. Contacting your State Health Insurance Assistance Program, known as SHIP, is a free way to get personalized counseling on your options. SHIP counselors are not insurance agents and have no financial incentive to steer you toward any particular plan — they exist solely to help Medicare beneficiaries understand their coverage.
The bottom line is this: Original Medicare Part A provides meaningful hospital coverage, but it is not comprehensive. The $1,676 per-benefit-period deductible, the daily coinsurance that begins at day 61, and the complete absence of an out-of-pocket maximum mean that a serious illness can generate bills that rival a year's worth of Social Security income. Understanding these numbers — and taking action during the appropriate enrollment windows to add supplemental coverage — is one of the most consequential financial decisions you can make as a Medicare beneficiary.