You spent a night in the hospital. You were in a room. You had nurses checking on you. Doctors came by. It felt exactly like you'd been "admitted."
Then the bill arrives, and you discover the hospital classified the visit as observation rather than inpatient admission. The dollar difference can be enormous — sometimes $10,000+ for the exact same care.
This isn't a mistake on the hospital's part. It's a billing distinction that hospitals make on purpose because of how Medicare and most commercial insurers pay. And it's increasingly common: between 2006 and 2020, observation stays at US hospitals tripled.
This guide explains what the difference is, why it matters financially, and what to do if you've been classified as observation when you should've been admitted.
The actual difference
Inpatient admission means a doctor signed an order specifically admitting you as an inpatient — usually because they expected you'd need at least two midnights of hospital care. Once admitted, your bill is paid under Medicare Part A (or your insurance's hospital benefit), which uses a single per-stay payment regardless of how long you're there.
Observation status means you're being held in the hospital for monitoring or short-term care, but a doctor hasn't formally admitted you. You're technically still an outpatient. Your bill is paid under Medicare Part B (or your insurance's outpatient benefit), which is per-service rather than per-stay.
The actual care you receive is often identical. You might be in the same kind of room, with the same nurses, getting the same medications. The difference is purely an administrative classification — and it can save the hospital money while costing you a lot more.
Why this costs you more money
Three concrete reasons.
1. Per-service billing instead of per-stay
Under observation, each test, IV push, drug administration, and bedside service is billed as a separate outpatient line item. You pay coinsurance on each one (often 20%). Under admission, you pay one inpatient deductible and that covers everything.
A 36-hour observation stay can produce 30-50 separate line items, each with its own coinsurance calculation. The total often exceeds the flat inpatient deductible by a wide margin.
2. Self-administered drugs aren't covered
Under observation (outpatient status), Medicare Part B does not pay for drugs you take yourself — like the daily medications a nurse hands you in a paper cup. The hospital bills you their full chargemaster price for these, often $20-$50 per pill. For routine medications you have at home for $5/month, this can add hundreds to a single stay.
3. It blocks Medicare's skilled nursing facility (SNF) benefit
This one's brutal for older patients. Medicare's SNF benefit (rehabilitation after a hospital stay — usually after surgery or a major illness) requires a 3-day inpatient admission first. If you spend 5 nights in observation, you don't qualify — and the average SNF stay costs $10,000+ out of pocket. Patients have lost their homes paying for SNF care because their hospitalization was classified observation instead of inpatient.
The "two-midnight rule"
In 2013, Medicare introduced the two-midnight rule to push hospitals toward admitting patients more aggressively. The rule: if a doctor expects the patient to need at least two midnights of hospital care, they should be admitted as inpatient. Less than that, observation is appropriate.
Hospitals get audited on this. If Medicare auditors find the hospital admitted someone who only stayed one night, they claw back the inpatient payment. So hospitals err on the side of observation when they're not sure.
The problem: doctors are often wrong about how long a patient will need. Someone admitted with chest pain who needs three days of testing might get classified observation on day one and never get re-classified when the stay extends.
How to tell which one you were
There are three places to look.
1. The discharge paperwork
Most hospitals are required to give you a written notice — called the Medicare Outpatient Observation Notice (MOON) if you have Medicare — within 36 hours of starting observation. The notice explicitly says "You are being treated as an outpatient under observation status." If you got that notice, you were observation.
If you didn't get it, ask the hospital for your admission status in writing.
2. The itemized bill
Look for the CPT code G0378 (observation per hour, hospital outpatient). If that's on the bill, you were observation. Inpatient stays have different codes (DRG-based, not CPT-based).
You may also see G0379 (direct admission to observation) and a slew of outpatient line items per nursing service.
3. The EOB
Your insurance's Explanation of Benefits will categorize the stay. Inpatient stays show under "hospital benefit" / "inpatient" / "Part A." Observation stays show under "outpatient benefit" / "Part B."
What to do if you should have been admitted
If you were observation but you genuinely needed two or more midnights of care AND your doctor agreed you needed admission-level care, you can appeal.
Step 1: Get the medical records. Specifically, you want the H&P (history and physical), progress notes, and any orders related to your admission status. You have a right to these under HIPAA.
Step 2: Ask the attending physician to write a letter stating that your care met inpatient criteria. Many doctors will do this if you ask politely; they often don't know about the financial impact on you.
Step 3: File a written reclassification request with the hospital's billing/medical-records department. Cite the two-midnight rule (42 CFR § 412.3) and the doctor's letter. Request reclassification to inpatient and a corrected bill.
Step 4: If they refuse, file a complaint with your state's department of health and (if Medicare) with the Quality Improvement Organization (QIO) in your state. QIOs handle observation-status appeals and can force the hospital to defend its classification.
You won't always win. But hospitals do reclassify when they're caught — and the dollar amount at stake is usually large enough to justify the effort.
What to demand on the bill even if you were correctly classified observation
Even if observation status was appropriate, there are still bill-reduction levers:
Packaged services should not be billed separately
Under CMS's Outpatient Prospective Payment System (OPPS), most observation-period ancillary services are packaged into the observation hourly rate. That means the following should NOT appear as separate line items:
- IV push administration (CPT 96374, 96375, 96376) during the observation period
- Basic monitoring (pulse oximetry CPT 94760, telemetry)
- Supplies and routine equipment
- Most surgical trays
- Lab draws (CPT 36415) during observation
If you see these on the bill in addition to the observation hours (G0378), the hospital is double-billing you for services that are already included in the observation rate. This is unbundling and CMS rules prohibit it.
Self-administered drugs at chargemaster prices
You can request the hospital provide self-administered drugs at the acquisition cost rather than chargemaster. They often will if asked. Or you can ask if a family member can bring your home medications to take during the stay.
Bring it up in writing
Hospitals have appeals processes. Most won't reduce a bill over the phone but will when faced with a clear, written demand citing CMS OPPS packaging rules.
How Audra spots observation-billing errors
When you upload a hospital bill to Audra, our auditor:
- Detects whether any G0378 (observation per hour) codes appear
- Flags any IV push, basic monitoring, supplies, or lab draw codes billed alongside observation as OPPS packaging violations
- Cross-references against CMS OPPS guidance (42 CFR § 419.2) in the appeal letter
We've seen observation bills with $300-$800 of improperly unbundled charges. The appeal letter we generate cites the specific CMS rules and demands removal of each one.
Your first audit is free. If you've had an observation stay and the bill feels too high, run it through Audra and we'll tell you exactly which charges shouldn't be there.