Part B outpatient surgery coverage affects millions of people with Medicare every year. More procedures now happen without a hospital stay than ever before. Cataract removal, colonoscopies, knee arthroscopy, and hernia repair are common examples. Many joint replacements now go home the same day too.
Medicare Part B pays for these procedures when they are medically necessary. However, your costs depend on where the surgery happens and how the facility bills it. Knowing how Part B outpatient surgery works helps you avoid surprise bills. It also helps you compare facilities, plan for coinsurance, and ask better questions before your procedure date.
How Medicare Part B Covers Outpatient Procedures
Medicare splits hospital care into two main parts. Part A covers inpatient stays after a formal admission. Part B covers outpatient services, including surgery that doesn’t require an admission. That is true even if you spend the night in a hospital bed. If no doctor writes a formal inpatient order, you remain an outpatient.
Part B covers outpatient surgery in two main settings. The first is a hospital outpatient department (HOPD). The second is an ambulatory surgical center (ASC), a freestanding facility built for same-day procedures. Both must be Medicare-certified. The procedure must also be medically necessary and ordered by a qualified provider.
Under Original Medicare, Part B outpatient surgery follows a standard cost structure. First, you meet the annual Part B deductible. After that, you typically pay 20% of the Medicare-approved amount. That 20% applies to the facility fee and to each doctor’s fee. Surgeons, anesthesiologists, and radiologists usually bill separately. As a result, one procedure can create several bills.
There is an important protection in hospital outpatient settings. For a single covered procedure, your HOPD copayment can’t exceed the Part A inpatient deductible for that year. This cap applies to the facility portion only. Doctor fees are still billed separately.
Part B Outpatient Surgery Costs: Hospital vs. Surgical Center
Where you have surgery matters. The same procedure can cost different amounts depending on the setting. CMS sets payment rates each year through two rules: the Outpatient Prospective Payment System (OPPS) and the ASC payment system. The final rules are usually released in early November. They take effect on January 1.
ASCs generally cost less than hospital outpatient departments. CMS pays ASCs a lower facility rate for most procedures. Your 20% share is based on that rate. So your out-of-pocket cost for Part B outpatient surgery is often lower at an ASC. For example, cataract surgery and many GI endoscopies usually cost beneficiaries less at a surgical center.
| Factor | Hospital Outpatient Department | Ambulatory Surgical Center |
|---|---|---|
| Part B deductible applies | Yes | Yes |
| Standard coinsurance | 20% of approved amount | 20% of approved amount |
| Facility payment level | Typically higher | Typically lower |
| Copay cap per procedure | Capped at Part A deductible | No comparable cap, but costs usually lower |
| Handles complex or high-risk patients | Yes, with full hospital backup | Limited to approved procedures |
| Separate doctor bills | Yes | Yes |
Not every procedure can happen at an ASC. CMS keeps an ASC Covered Procedures List. Only procedures on that list are paid in an ASC setting. CMS has expanded the list in recent years. It now includes some total knee replacements, hip replacements, and certain cardiac procedures.
CMS also keeps an “inpatient only” list. Procedures on it are paid only after a formal hospital admission. In the 2026 OPPS final rule, CMS began a three-year phase-out of this list. It started with a large group of mostly musculoskeletal procedures. As a result, more surgeries may qualify for outpatient billing in coming years.
Some costs fall outside Part B entirely. Self-administered drugs given in a hospital outpatient setting are generally not covered by Part B. That can include routine pills you normally take at home. The hospital may bill you directly. Your Part D plan may reimburse some of it, but only if you file a claim.
Steps to Take Before Your Procedure
Preparation can lower your bill. It can also prevent coverage problems. Start with these steps a few weeks before Part B outpatient surgery.
1. Check the price. Use the Procedure Price Lookup tool on Medicare.gov. It shows national average costs for many procedures in both HOPDs and ASCs. It also estimates your share after Original Medicare pays. Actual costs vary by location and by doctor.
2. Confirm your status. Ask the hospital directly whether you are an inpatient or an outpatient. Observation stays count as outpatient care. If you are under observation for more than 24 hours, the hospital must give you a Medicare Outpatient Observation Notice (MOON). Outpatient status affects your costs. It also affects skilled nursing facility coverage later, which requires a qualifying three-day inpatient stay.
3. Verify that providers accept assignment. Doctors who accept assignment agree to take Medicare’s approved amount. Non-participating doctors can charge up to 15% more. Ask each provider on your surgical team, including the anesthesiologist.
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4. Review Medicare Advantage rules. Plans from UnitedHealthcare, Humana, Aetna, Cigna, and Blue Cross often require prior authorization. Many also require in-network facilities. Copays in Medicare Advantage plans follow the plan’s own schedule, not Original Medicare’s 20% rule. Call your plan before scheduling. Get any approval in writing.
5. Understand your supplemental coverage. A Medigap policy can cover most or all of your 20% coinsurance. Plan G and Plan F pay the full Part B coinsurance. Plan N covers most of it but allows small office copays. Insurers such as AARP/UnitedHealthcare and Mutual of Omaha sell Medigap policies in most states. Pricing varies by state and insurer.
6. Review your Medicare Summary Notice. After surgery, check your MSN carefully. Compare it against every bill. Look for duplicate charges or services you did not receive. You have 120 days from the date you receive the notice to file an appeal.
Free help is available. Your State Health Insurance Assistance Program (SHIP) offers unbiased counseling at no cost. SHIP counselors can explain billing, compare plans, and help with appeals. You can also call 1-800-MEDICARE with coverage questions.
Frequently Asked Questions
Does Medicare pay for outpatient surgery at a surgical center?
Yes. Part B covers approved procedures at Medicare-certified ambulatory surgical centers. You typically pay 20% after meeting the Part B deductible. In most cases, ASC costs are lower than hospital outpatient costs.
Is an overnight observation stay covered under Part B?
Yes, observation is billed as outpatient care under Part B. You may owe copays for each service and for self-administered drugs. For example, a two-night observation stay still counts as outpatient care unless a doctor formally admits you.
What does Part B outpatient surgery cost with a Medigap plan?
With Medigap Plan G, you usually pay only the annual Part B deductible. The plan then covers the 20% coinsurance. In most cases, Plan F enrollees owe nothing, but Plan F is only available to people eligible for Medicare before 2020.
Does Medicare Advantage cover outpatient surgery the same way?
Medicare Advantage plans must cover everything Original Medicare covers. However, costs and rules differ. Most plans use fixed copays, network requirements, and prior authorization for Part B outpatient surgery.
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Official Sources & Resources
For verified information on Medicare regulations and consumer protection:
- Medicare.gov (Official Site): medicare.gov
- CMS (Centers for Medicare & Medicaid Services): cms.gov
- NAIC (National Association of Insurance Commissioners): naic.org
- KFF Medicare Research: kff.org/medicare
- Social Security Administration: ssa.gov
Content last reviewed September 2026. If you notice any outdated information, please contact us.