Medicare Part A

Medicare Part A is the component of Medicare that pays for institutional care. Congress named it Hospital Insurance, and 42 U.S.C. 1395c describes it as basic protection against the costs of hospital, post-hospital, home health and hospice care. The benefits themselves are set out at 42 U.S.C. 1395d: inpatient hospital services, post-hospital extended care services in a skilled nursing facility, home health services, and hospice care. Medicare's own consumer materials label it "Part A (Hospital Insurance)", and the trust fund that pays for it is the Hospital Insurance trust fund, so both names describe the same coverage.

One naming difference is worth knowing before reading any of the rules. The statute measures Part A's benefits in a unit it calls a spell of illness; Medicare's consumer materials call the same unit a benefit period. They are the same thing under two names, and almost everything that surprises people about Part A follows from how that unit is defined.

The benefit period is the whole trick. Under 42 U.S.C. 1395x(a), a spell of illness begins with the first day on which the beneficiary is furnished inpatient hospital or skilled nursing facility services, and it ends with the close of the first period of 60 consecutive days on each of which they are an inpatient of neither. Because Part A's deductible is charged once per benefit period, a beneficiary who is hospitalized in February, discharged, and hospitalized again in July pays two full deductibles in one calendar year. Someone readmitted three weeks after discharge pays one, because the original benefit period never closed. No other part of Medicare works this way; Part B's deductible is annual.

One detail inside that definition catches families out in the opposite direction. Still living in a nursing home does not keep the benefit period open indefinitely. Under 42 C.F.R. 409.60(b)(2) a resident counts as an inpatient of a skilled nursing facility, for the purpose of ending a benefit period, only while their care actually meets the skilled level-of-care test. Once it drops to custodial help with daily activities, the 60-day clock runs even though nobody has gone home, which is usually good news: a later hospital admission then opens a fresh 90 days.

Day counts, and the reserve that never comes back. The statute provides inpatient hospital coverage for up to 150 days in a spell of illness, reduced by one day for each day of such services in excess of 90 received during any preceding spell. In consumer terms that is 90 days per benefit period plus a lifetime reserve of 60 days, and the reserve is drawn down permanently: a day used in 2027 is not available in 2035. Skilled nursing facility care runs up to 100 days per benefit period.

The daily amounts change every year, but the ratios behind them do not, and knowing the ratios is more useful than memorising a figure. Under 42 C.F.R. 409.83 and 409.85 every daily charge is a fixed fraction of that year's inpatient hospital deductible. There is no daily coinsurance for the first 60 inpatient days, then one quarter of the deductible for days 61 to 90, and one half of it for each lifetime reserve day. Skilled nursing care charges nothing for the first 20 days and one eighth of the deductible for days 21 to 100. So a reserve day costs exactly twice a day in the 61-to-90 band, and the whole schedule moves in step with the deductible.

Two mechanics worth knowing before a long stay rather than after. First, the beneficiary can decline to use lifetime reserve days. Under 42 C.F.R. 409.65 an election not to use them keeps them available for a later stay, and the regulation names the cases for considering it: private insurance that begins after day 90, or a hospital charge barely above the reserve-day coinsurance. It is a trade rather than a free option, because the hospital may then bill for those days directly. Second, cost-sharing is not frozen at the rates in force when the benefit period opened. Under 42 C.F.R. 409.82(a)(4) and 409.83(a)(5) both the deductible and each day's coinsurance are set by the calendar year the care was furnished in, so a stay long enough to reach coinsurance days on both sides of New Year is billed at two different daily rates.

The skilled nursing prerequisite catches people who did nothing wrong. What Part A actually covers is "post-hospital extended care services", which 42 U.S.C. 1395x(i) defines as care furnished after transfer from a hospital "in which he was an inpatient for not less than 3 consecutive days before his discharge". The three days must be inpatient days. Time spent in a hospital under observation status is outpatient care, however many nights it involves and however indistinguishable it feels from admission, so it does not count toward the three. A patient can spend four nights in a hospital bed and still fail the test. Asking whether a stay has been formally converted from observation to inpatient is therefore a practical question, not a technicality.

Premium-free is a work-record rule, not a universal one. Entitlement under 42 U.S.C. 1395c runs through eligibility for Social Security retirement benefits, and 42 U.S.C. 414(a)(2) defines a fully insured individual as one credited with 40 quarters of coverage, roughly ten years of covered work. CMS, the federal agency that administers Medicare, puts the share of beneficiaries who pay no Part A premium at approximately 99 percent. The remainder are covered by a whole separate statutory section, 42 U.S.C. 1395i-2, headed "Hospital insurance benefits for uninsured elderly individuals not otherwise eligible". Buying in requires being 65 or over, enrolled in Part B, a United States resident, and either a citizen or a lawful permanent resident of at least five years' continuous residence. There are two premium tiers, and the discount is a statutory percentage rather than a figure that has to be looked up: someone credited with at least 30 quarters of coverage pays the full premium reduced by 45 percent, and someone below 30 quarters pays it in full. The 30-quarter test can be met through a spouse as well as personally, including a widow or widower after a year of marriage and a divorced person after ten years of it. Part B enrollment is not merely an entry condition: dropping Part B ends the bought-in Part A coverage at the same time, so this route cannot be used to hold hospital coverage on its own.

1. A benefit period opens on the first day of inpatient hospital or skilled nursing facility care.

2. The Part A deductible is charged once for that benefit period.

3. Inpatient days accumulate: no daily coinsurance through day 60, a daily amount for days 61 to 90, then lifetime reserve days at a higher daily amount, up to 60 such days across the beneficiary's whole life.

4. Skilled nursing care, if it follows an inpatient hospital stay of at least three consecutive days, runs up to 100 days in the benefit period, free of daily coinsurance for the first 20 and charged daily from day 21.

5. The benefit period closes only after 60 consecutive days with no inpatient hospital or skilled nursing stay. Care after that starts a new benefit period, with a new deductible and a fresh day count.

A hypothetical, using days rather than dollars. Ruth is admitted on 3 March, discharged on 12 March, and pays one Part A deductible. She has no inpatient hospital or skilled nursing care from 13 March onward, so the 60-day clock runs from 13 March to 11 May (19 days in March, 30 in April, 11 in May) and her benefit period closes on 11 May. A readmission on 2 June therefore starts a new benefit period: day count back to one, and a second full deductible in the same calendar year. Change one fact and the answer inverts. Had she been readmitted on 20 April, only 38 days would have passed, the benefit period would still have been open, the April stay would have continued her existing day count instead of restarting it, and there would have been no second deductible.

Part A's deductible, its daily coinsurance amounts, the lifetime reserve day rate and the two buy-in premiums are all reset annually. The coinsurance figures are required to be published in the Federal Register by 1 October for the following calendar year, and CMS publishes the whole set each autumn. This entry states the structure and the ratios and deliberately leaves the amounts to medicare.gov.

Pros

• Premium-free for the large majority of beneficiaries, having been prepaid through decades of payroll tax.
• No underwriting and no health questions: entitlement is statutory.
• Covers the most catastrophic category of expense, a long inpatient stay, with a deductible that is small relative to the bill.
• Hospice coverage is unusually open-ended: two 90-day election periods followed by an unlimited number of 60-day periods, with no lifetime cap. It is also the benefit Original Medicare keeps paying for even when the beneficiary is enrolled in a Medicare Advantage plan. The statute provides it "in lieu of certain other benefits", so electing hospice means giving up Medicare coverage of curative treatment for the terminal illness.

Cons

• The per-benefit-period deductible means an unlucky year with two separated hospitalizations costs twice what most people expect.
• Lifetime reserve days are finite and never replenish.
• The three-day inpatient prerequisite for skilled nursing care turns on how a hospital classified a stay, which the patient often does not control and is not always told.
• Part A pays nothing toward physician bills, outpatient care, or drugs taken at home, so it is not usable on its own as health coverage.
• It does not cover long-term custodial care at all, which is the expense most often assumed to be a hospital-type risk.