Here's the short answer. You are an inpatient only after a doctor writes an order to formally admit you. You are an outpatient under "observation status" while the doctor decides whether to admit you or send you home. That's true even if you spend the night in a regular hospital bed. The label matters for two reasons. Inpatient care is billed to Part A, while observation care is billed to Part B. And only inpatient days count toward the 3-day hospital stay Medicare requires before it pays for a skilled nursing facility.
What observation status means
Observation services are hospital outpatient services you get while your doctor decides whether to admit you as an inpatient or discharge you. You can get them in the emergency department or in another part of the hospital.
Your status starts as outpatient. It changes only when the doctor orders an inpatient admission and the hospital formally admits you. As a rule of thumb, inpatient admission fits when the doctor expects you to need hospital care for two or more midnights. Until that order is written, everything — the ER visit, tests, an overnight stay in observation — is outpatient care.
If you get observation services for more than 24 hours, the hospital must give you a written notice. It's called the Medicare Outpatient Observation Notice (MOON). It explains why you're an outpatient, not an inpatient. It also explains how that may affect what you pay — in the hospital and for care after you leave. A 2015 federal law (the NOTICE Act) requires this notice.
How each status is billed
With Original Medicare, the split works like this:
- Inpatient: Part A pays for the hospital stay itself. For most hospitals, Part A also covers related outpatient services from the 3 days before your admission date. Part B pays your doctors' services. Part A costs work by benefit period, starting with the Part A deductible.
- Outpatient (including observation): Part A pays nothing. Part B pays for your doctors' services and each hospital outpatient service. You usually owe 20% of the Medicare-approved amount after the Part B deductible. You also pay the hospital a copayment for each service.
There is a partial guardrail. The copayment for a single outpatient service can't be more than the Part A inpatient hospital deductible. But your total copayments across all the services in an observation stay can add up to more than that.
Watch for one more outpatient surprise: your regular prescription drugs. Part B generally doesn't cover "self-administered drugs" — the pills you'd normally take at home — when you get them as a hospital outpatient. If you have Part D, you'll likely pay the hospital out of pocket, then send a claim to your drug plan for a refund. Our costs guide explains deductibles, coinsurance, and copayments in plain terms.
The biggest risk: skilled nursing facility coverage
This is where observation status hurts the most. Medicare covers a stay in a skilled nursing facility (SNF) only after a "qualifying inpatient hospital stay." That means a medically necessary inpatient stay of at least 3 days in a row. The count starts the day you're formally admitted as an inpatient. It doesn't include the day you leave.
Time spent under observation or in the emergency room before admission does not count toward those 3 days — even if you're there overnight. So a person can spend several nights in a hospital bed, then move to a nursing facility to recover. If those hospital nights were "observation," Medicare won't pay for the facility.
Two more rules apply to SNF coverage. You generally must enter the facility within a short time (usually 30 days) of leaving the hospital. And your doctor must decide you need daily skilled care. See what Medicare does and doesn't cover for nursing home care for the bigger picture.
Two exceptions are worth asking about. Some doctors are part of an Accountable Care Organization with an approved "SNF 3-Day Rule Waiver" — then the 3-day stay may not be required. Medicare Advantage plans may also waive the 3-day rule. Their costs and rules for hospital status can differ from Original Medicare, so check with the plan.
If the hospital changes your status
Sometimes a hospital admits you as an inpatient and then, before discharge, switches you to "outpatient getting observation services." Your doctor must agree. The hospital must tell you in writing before you leave.
Since February 14, 2025, that switch comes with a new appeal right. You should get a "Medicare Change of Status Notice" (form CMS-10868) before you leave. It explains that your stay will be billed to Part B instead of Part A. It warns that Medicare won't pay for a skilled nursing facility after this stay. And it tells you how to ask for a fast appeal through your state's Quality Improvement Organization (called a BFCC-QIO).
File while you're still in the hospital if you can. You can still appeal after you leave. The BFCC-QIO reviews your medical records and decides about 2 days after you file. If you win, your stay counts as inpatient — and you may qualify for Medicare-covered SNF care within 30 days of discharge.
You may even be able to appeal old stays. Medicare allows appeals of these status changes for hospital stays going back to January 2009. For how Medicare appeals work in general, see appeal levels and timelines and your rights and protections.
What you can do during a hospital stay
- Ask your status every day. Status can change during a stay. Ask the doctor, a nurse, or the hospital's case manager or patient advocate.
- Read every notice you're handed. The MOON and the Change of Status Notice aren't routine paperwork — they're the official word on how your stay will be billed.
- If a nursing facility is likely next, raise it early. Ask the doctor and hospital staff whether Medicare will cover the SNF stay.
- Bring your drug plan card, and ask how the hospital bills your regular medications if you're an outpatient.
- Get free help. Your State Health Insurance Assistance Program (SHIP) can walk you or your caregiver through status questions and appeals at no charge.
Common questions
I stayed two nights in a hospital bed. Doesn't that make me an inpatient?
Not by itself. You're an inpatient only after a doctor writes an order to admit you. Without that order, even an overnight stay in a regular hospital bed is outpatient care.
Does observation time ever count toward the 3-day stay for nursing facility coverage?
No. Time under observation or in the ER before you're formally admitted doesn't count, even overnight. Only inpatient days count. The count starts the day you're admitted and doesn't include the day you leave.
Will the hospital tell me I'm under observation?
Yes, if it lasts more than 24 hours. Federal law requires the hospital to give you the Medicare Outpatient Observation Notice (MOON) explaining your outpatient status and what it means for your costs. Don't wait for the notice, though — ask your status every day.
Do these rules apply to Medicare Advantage plans?
Costs and coverage may be different in a Medicare Advantage plan. Some plans waive the 3-day inpatient stay rule for skilled nursing facility coverage. Check with your plan. Prior authorization rules may also apply — see how Medicare Advantage prior authorization works.
Can I fight an observation classification?
If you were admitted as an inpatient and the hospital changed you to observation, yes. Since February 14, 2025 you can ask your BFCC-QIO for a fast appeal. Appeals are allowed for stays going back to January 2009. Follow the instructions on your Medicare Change of Status Notice (CMS-10868). If you were never admitted as an inpatient at all, there's no fast-appeal path for that choice. Talk with the doctor about whether inpatient admission fits your case, and get free help from your SHIP.
Official sources
- Medicare.gov: Inpatient or outpatient hospital status affects your costs
- Medicare.gov: Skilled nursing facility (SNF) care
- Medicare.gov: Appeal a hospital status change
- CMS.gov: Medicare Outpatient Observation Notice (MOON)