How does Medicare coverage affect length of stay in a skilled nursing facility?

1. How Medicare’s “100-day” limit actually works — the benefit-period framing

Medicare counts SNF coverage in the context of a “benefit period,” which begins the day you are admitted as an inpatient to a hospital or SNF and ends when you’ve been out of inpatient care for 60 consecutive days; within each benefit period Medicare will cover up to 100 days of SNF care if all conditions are met ^{[2] [6]}. That means someone could potentially have more than 100 covered SNF days over multiple benefit periods, but they must trigger a new benefit period by going 60 days without inpatient care ^{[1] [2]}.

2. What Medicare pays across days 1–100 — money and requirements

If Medicare approves the stay, it pays 100% of covered SNF costs for days 1–20 (after the Part A deductible is met), then requires a daily coinsurance payment for days 21–100 (examples cited: $209.50 per day in 2025 in multiple sources) ^{[1] [3] [7]}. Coverage is contingent on meeting the 3-day hospital inpatient requirement, needing skilled care that must be provided in an SNF, and having a doctor certify daily skilled care or therapy is necessary ^{[5] [4] [8]}.

3. What happens after day 100 — the coverage cliff

After 100 days in a benefit period, Original Medicare Part A stops covering SNF care regardless of ongoing medical need; patients are responsible for all costs unless they have supplemental coverage, transition to Medicaid, or another payer takes over ^{[9] [7]}. Sources repeatedly call the 100-day limit “time-limited” and warn families about the financial and care-planning implications ^{[9] [7] [10]}.

4. How the “3-day rule” and medical necessity shape length of stay

Medicare’s linkage of SNF coverage to a qualifying hospital stay (commonly called the 3-day rule) directly affects whether SNF days will be paid at all; time spent under observation or in the emergency department typically does not count toward that qualifying stay ^{[4] [11]}. Even after meeting the 3-day requirement, Medicare can stop paying if a patient no longer meets criteria for “skilled” care — facilities must issue notices if Medicare will stop coverage ^[8].

5. Average stays and payer-driven behavior — what influences actual length of stay

Although the program caps coverage at 100 days, most Medicare-covered SNF stays are much shorter in practice; some providers report typical stays of two to three weeks (about 14–21 days), reflecting clinical recovery patterns and incentives ^[12]. Meanwhile, recent reporting and research suggest plan type affects timing: Medicare Advantage patients have experienced longer pre-SNF hospital stays and other discharge-pattern shifts that can indirectly change time in SNFs and admission timing ^{[13] [14]}.

6. Practical consequences and alternative payment routes

Because Medicare’s SNF benefit is short-term by design, families planning for longer rehabilitation or custodial care often must consider Medicaid, long-term care insurance, private pay, or supplemental Medigap policies that can cover coinsurance days 21–100 ^{[7] [8]}. Several sources warn that once Medicare stops paying, patients can face steep private rates and must explore state-specific Medicaid rules or other funding options ^{[7] [9]}.

7. Limits of available reporting and remaining questions

Available sources clearly document the 100-day cap, the 3-day hospital rule, day-by-day cost sharing, and the benefit-period mechanics ^{[1] [2] [5]}. What the provided reporting does not mention in detail are national statistics on how many patients actually exhaust the full 100 days, granular regional cost comparisons after day 100, or exhaustive differences across Medicare Advantage plan contracts — those points are not found in current reporting among these sources (not found in current reporting).

Takeaway: Medicare frames SNF coverage as short, conditional, and cyclical — it pays for most short rehabilitation stays (especially days 1–20), shifts costs to beneficiaries during days 21–100, and stops at day 100 unless another payer or program covers the remainder, while hospital-qualification rules and plan type materially affect how and when that coverage applies ^{[1] [2] [3]}.