How Medicare Covers Outpatient Surgery at an ASC

Medicare Part B covers outpatient surgery at certified ASCs

Medicare Part B — medical insurance, not hospital insurance — is what covers outpatient surgery. This includes procedures at Medicare-certified ambulatory surgery centers. Part A (hospital insurance) is for inpatient stays and is generally not involved in ASC care.

Medicare pays a fixed facility fee directly to the ASC

CMS sets an ASC payment rate for each covered procedure code. The facility bills Medicare, Medicare pays its share, and the remainder is your responsibility. The ASC rate is the same nationally (with a small geographic adjustment) — it doesn't vary based on what the facility wants to charge.

ASC rates are lower than hospital outpatient rates for the same procedure

CMS intentionally pays ASCs less than hospital outpatient departments — currently around 60–65% of the hospital rate. This is the source of the cost savings for patients. When you have a procedure at an ASC, both Medicare and you pay less.

The Part B deductible applies first

In 2025, the Medicare Part B deductible is $257 per year. Once you've met it, Medicare pays 80% of the approved amount for covered services. You owe the remaining 20%.

You owe 20% of the Medicare-approved ASC facility fee

After the deductible, your share is 20% of the ASC facility fee — not 20% of what the facility wants to charge. Medicare determines the approved amount, and coinsurance is based on that figure. For a procedure where Medicare pays $800, your share would be $160.

Medigap (Medicare Supplement) may cover your 20%

If you have a Medigap policy, it may cover some or all of the 20% coinsurance, depending on your plan letter. Plan G, for example, covers the Part B coinsurance after the deductible. Check your specific plan.

Medicare Advantage plans have different cost structures

If you have a Medicare Advantage (Part C) plan, your ASC costs depend on your plan's benefit design — copays, coinsurance rates, and network requirements vary. Check your Evidence of Coverage document or call your plan.

The surgeon and anesthesiologist bill separately

The facility fee is one line item. Your surgeon bills their professional fee separately under Part B as well, and the anesthesiologist does the same. Each is subject to the same deductible and coinsurance rules, but they're separate claims.

CMS maintains an approved list of covered ASC procedures

Not every procedure can be billed under the ASC benefit. CMS publishes an annual list of procedures approved for the ASC payment system. This list has expanded significantly over time as technology has made more procedures suitable for outpatient settings.

Colonoscopies, cataracts, joint procedures — all covered

The most common ASC procedures — colonoscopy, cataract surgery, knee and shoulder arthroscopy, carpal tunnel release, hernia repair, ENT procedures — are all on the approved list and covered under Part B.

Some procedures aren't covered in any outpatient setting

Medicare doesn't cover cosmetic procedures regardless of setting. Certain experimental or investigational procedures are also excluded. If you have questions about a specific code, ask the ASC's billing department before scheduling.

Confirm the facility is Medicare-certified

All facilities in this directory are Medicare-certified, but verify directly with the facility if you're scheduling elsewhere. An uncertified facility cannot bill Medicare — and you'd be responsible for the full cost.

Confirm your surgeon and anesthesiologist accept Medicare assignment

Accepting assignment means the provider agrees to accept Medicare's approved amount as payment in full (minus your deductible and coinsurance). Providers who don't accept assignment can charge up to 15% more than the approved amount.

Ask about the procedure code before scheduling

If you want to estimate your out-of-pocket cost, ask the facility for the primary CPT code for your procedure. You can look up the Medicare ASC rate on the CMS website, then calculate 20% of that to estimate your facility fee share.