Medicare covers hospital observation stays under Part B (outpatient coverage), not Part A (inpatient coverage). That distinction matters more than most people realize. You’ll typically owe the 2025 Part B deductible of $257 plus 20% of the Medicare-approved amount for each covered service, and you may face additional charges for medications. The total out-of-pocket cost for an observation stay can range from a few hundred to several thousand dollars depending on what tests, treatments, and drugs you receive.
Why Observation Is Outpatient, Not Inpatient
Even though you’re lying in a hospital bed, possibly overnight, observation is classified as outpatient care. Hospitals follow what’s known as the Two-Midnight rule when deciding your status. If your doctor expects you’ll need hospital care spanning at least two midnights, you’re generally admitted as an inpatient under Part A. If the expected stay is shorter than that, you’re typically placed in observation status under Part B.
This decision is based on the physician’s clinical judgment at the time of your arrival. A hospital can keep you in observation while doctors run tests, monitor your symptoms, and decide whether you’re well enough to go home or sick enough to be formally admitted. Most observation stays last less than 24 hours, and claims exceeding 48 hours may trigger a review by Medicare.
What You’ll Pay Out of Pocket
Because observation falls under Part B, your costs look different from an inpatient stay. First, you’ll need to meet the annual Part B deductible, which is $257 in 2025. After that, you’ll owe 20% of the Medicare-approved amount for each covered service you receive during your stay. That includes doctor visits, lab work, imaging, IV medications, and the observation services themselves.
There’s no single flat fee for an observation stay. Your bill is the sum of every individual service provided. A straightforward observation stay with basic monitoring and blood work will cost far less than one involving CT scans, cardiac monitoring, and specialist consultations. The hospital also charges a copayment for each outpatient service, though in most cases that copayment won’t exceed the Part A inpatient deductible amount.
For comparison, an inpatient stay under Part A has a single deductible of $1,676 in 2025 that covers up to 60 days, with no coinsurance percentage on individual services. So while observation sounds cheaper on paper, a longer or more complex observation stay can sometimes cost a patient more than a standard inpatient admission would have.
The Medication Surprise
One of the most frustrating costs during observation involves your regular medications. Part B generally does not cover self-administered drugs in an outpatient hospital setting. These are the everyday pills you take at home for things like blood pressure, diabetes, or cholesterol. If you need those medications during your observation stay, the hospital may charge you directly for them, often at prices well above what you’d pay at a pharmacy.
If you have a Medicare Part D drug plan, it may reimburse some of that cost, but typically only at the in-network pharmacy rate minus your normal copay. You could still owe the difference between what the hospital charged and what your drug plan paid. Drugs administered by hospital staff through an IV are covered under Part B, but anything you’d normally swallow on your own is treated differently. Bringing your own medications from home is worth asking about, though hospital policies vary.
The Skilled Nursing Facility Problem
This is where observation status hits hardest. Medicare only covers care in a skilled nursing facility if you first have a qualifying inpatient hospital stay of at least three consecutive days. Time spent in observation does not count toward those three days, even if you were physically in the hospital for a week. Neither does time in the emergency room before observation began.
So if you spend two days in observation and then one day as a formal inpatient, you have only one qualifying inpatient day, not three. If you’re discharged and need rehab or skilled nursing care, Medicare won’t cover it. This can leave patients and families facing skilled nursing costs of several thousand dollars per month entirely on their own. It’s one of the most significant financial consequences of observation status, and it catches many people off guard.
How Medicare Pays the Hospital
Medicare pays hospitals for observation through the Outpatient Prospective Payment System. When an observation stay meets certain criteria, it qualifies for a bundled payment called Comprehensive Observation Services. To qualify, the stay must include at least 8 hours of observation, be linked to an emergency department visit or direct admission, and not involve a major procedure. When those conditions are met, Medicare makes a single comprehensive payment to the hospital that bundles the observation hours with the other outpatient services provided during the visit.
For shorter or less complex observation stays that don’t meet the bundled threshold, Medicare pays the hospital separately for each individual service. Either way, your 20% coinsurance is calculated based on what Medicare approves for those services.
Your Right to Be Notified
Hospitals are legally required to tell you if you’re in observation status. Under the NOTICE Act, any hospital must provide a written Medicare Outpatient Observation Notice (known as a MOON) to patients who have been in observation for more than 24 hours. The notice must be delivered no later than 36 hours after observation begins, or upon discharge if that comes sooner. A staff member must also explain the notice to you verbally, and you’ll be asked to sign acknowledging you received it.
The notice explains that you are an outpatient, not an inpatient, and outlines what that means for your costs and future coverage. If you’ve been in a hospital bed overnight and haven’t been told your status, ask directly. You have the right to know, and knowing early gives you or your family time to discuss the decision with your doctor. Physicians can change your status to inpatient if your condition warrants it and the medical record supports an expected stay of two midnights or more.
Medicare Advantage Plans
If you’re enrolled in a Medicare Advantage plan (Part C) rather than Original Medicare, your costs for observation may look different. These private plans must cover at least what Original Medicare covers, but they set their own copay and coinsurance structures. Some plans charge a flat copay per observation stay rather than the 20% coinsurance model. Others may have different rules around which services require prior authorization. Check your plan’s Evidence of Coverage document or call the plan directly to understand your specific cost-sharing for outpatient observation. There is limited published data comparing observation costs between Medicare Advantage and Original Medicare, so your plan’s specifics matter.