The short version

Observation is a billing classification, not a place. Same bed, same gown, same nurses — different category on the paperwork.
Observation nights do not count toward the three inpatient days Medicare requires before it will cover a skilled nursing facility stay.
One appeal route is still open and one has closed. If the patient is still in the hospital, a fast appeal is available now. The retrospective window closed on 2 January 2026.
Ask while they are still admitted. Almost everything about this gets harder after discharge.

A woman spends Monday, Tuesday and Wednesday night in a hospital. She has a bed, a wristband, a chart, and nurses checking on her hourly. On Thursday she is discharged to a skilled nursing facility for rehabilitation, and a few weeks later a bill arrives for thousands of dollars that Medicare will not pay.

Nothing went wrong medically. She was never an inpatient.

What is Medicare's three-day rule?

Traditional Medicare will only cover a skilled nursing facility stay if it follows a qualifying inpatient hospital stay of at least three consecutive days. The day of discharge does not count toward the three.

The word doing all the work is inpatient. Being in a hospital is not the same as being admitted to one. A patient can occupy a bed for three nights as an outpatient receiving observation services, and from Medicare's perspective those nights simply are not inpatient days.

Observation is not a lesser standard of care and it is not a different ward. It is a classification applied to the stay for billing purposes, usually when the team is deciding whether someone is sick enough to need admission or well enough to go home. The care can be identical. The coverage consequences are not.

What does observation status cost?

Observation status changes the bill in three separate ways, and families usually only discover the third.

The hospital stay bills under Part B, not Part A. That means a share of the cost for each individual service rather than a single inpatient deductible.
Routine medications may not be covered. Drugs given during an outpatient stay are often billed separately, including ones the patient takes at home every day.
The skilled nursing stay is not covered at all. No qualifying inpatient stay means no Part A coverage for rehabilitation, and the facility bills privately. This is the one that runs to five figures.

Where you actually stand

The status question has a small number of possible answers, and each leads somewhere different.

Was the patient formally admitted as an inpatient at any point?
- No — observation the whole time
  Those nights do not count toward the three-day requirement, however many there were.
  
  Important limit: the appeal right created by Alexander v. Azar applies to people who were admitted as inpatients and then reclassified. Someone placed under observation from the start is not covered by it. Ordinary Medicare appeal routes still exist, and a State Health Insurance Assistance Program can help.
- Yes — and the status never changed
  Those are inpatient days. Three consecutive ones, not counting the discharge day, satisfy the requirement.
  
  Nothing to appeal. Confirm the dates on the discharge paperwork before the patient transfers.
- Yes — but the hospital changed it to observation during the stay
  This is the situation the courts addressed, and where a real appeal right exists.
  
  Still in the hospital? A fast appeal has been available since February 2025. The hospital must issue a Medicare Change of Status Notice, and the appeal is filed before discharge.
  
  Already discharged? The retrospective route closed on 2 January 2026. Late requests are denied as untimely unless good cause — serious illness, incapacity, a death in the family, a catastrophic event — is shown.

What is the MOON notice?

Hospitals are required to give a Medicare Outpatient Observation Notice — the MOON — to patients receiving observation services for more than 24 hours. It states in writing that the patient is an outpatient and explains what that means for cost.

It arrives in a folder of admission paperwork during one of the more stressful days of someone's life, and it is regularly signed without being read. If you are sitting with a family member in a hospital, that single sheet is worth finding.

Since February 2025 there is a second notice: the Medicare Change of Status Notice, issued when a hospital reclassifies an admitted inpatient to observation. That one carries appeal rights that must be exercised before the patient leaves.

From the other side of it

By the time this becomes visible to me, the patient is already in the facility and the classification is weeks old. The window where anything could have been done cheaply has usually closed.

Experience rather than evidence, and worth labelling as such — but consistent enough to state plainly: the question is she admitted as an inpatient, or under observation? is worth asking on day one of a hospital stay, of any patient who might need rehabilitation afterwards. It takes ten seconds and it is the highest-leverage question in this entire article.

Can you appeal observation status?

Sometimes — and one route has closed. In 2020 a federal court held in Alexander v. Azar that patients admitted as inpatients and later reclassified to observation have a constitutional due-process right to appeal. An appeals court affirmed it in 2022, and CMS published implementing regulations in October 2024.

Two routes came out of that, and they are in different states today:

Prospective, or "fast," appeals — open. Available since 14 February 2025 for patients still in the hospital who receive a Change of Status Notice.
Retrospective appeals — closed. The filing period for past stays ended on 2 January 2026. Requests received after that are denied as untimely unless good cause for late filing is established.

Plenty of material online still describes the retrospective route as though it were open. If a family member is researching a hospital stay from 2023, that advice is now out of date — the remaining path is a good-cause late filing, which is a narrower and more demanding thing.

What to ask, and when

On day one: Is she admitted as an inpatient, or is she under observation?
If observation: What would need to change for her to be admitted?
If the answer shifts mid-stay: ask for the Change of Status Notice in writing, and ask about the fast appeal before discharge.
Before any transfer: How many inpatient days does the record show? Get the dates.
If a skilled nursing stay is likely: raise the three-day question with the hospital case manager while there is still time for it to matter.

None of this requires arguing with anyone. It requires asking early, in a system where the classification is often settled before anyone thinks to mention it.

This article is general education about Medicare coverage rules and how hospital status classifications work. It is not medical or legal advice, does not create a patient–provider relationship, and cannot account for an individual situation. Rules differ under Medicare Advantage. For a specific case, contact the hospital's case management team, your State Health Insurance Assistance Program, or 1-800-MEDICARE. See the editorial policy for how this content is written and reviewed.

Sources

Centers for Medicare & Medicaid Services. Hospital Appeals — Change of Inpatient Status (Alexander v. Azar). Eligibility, the prospective and retrospective processes, and the 2 January 2026 close of the retrospective filing period. Page last modified 27 March 2026.
Medicare.gov. Skilled nursing facility (SNF) care. The qualifying inpatient stay requirement.
Centers for Medicare & Medicaid Services. Medicare Outpatient Observation Notice (MOON). The notice hospitals must deliver for observation stays exceeding 24 hours.
Center for Medicare Advocacy. Frequently asked questions about the observation status court decision. Class counsel in Alexander v. Azar.