Ambulatory surgery centers: what U.S. patients should know

If your doctor recommends an outpatient procedure, you may be told that it will take place at an ambulatory surgery center. You may also hear the terms ASC, same-day surgery center, or outpatient surgery center.

An ASC provides a focused setting for procedures that usually do not require hospital admission. Most patients arrive, have their procedure, recover under medical supervision, and return home on the same day.

Before scheduling your procedure, make sure you understand why your doctor recommends the ASC, how your insurance may cover the service, what you may need to pay, and how to prepare for a safe recovery.

What is an ambulatory surgery center?

An ambulatory surgery center is a healthcare facility that performs surgeries and procedures for patients who are not expected to need hospitalization.

The Centers for Medicare and Medicaid Services defines an ASC as a distinct facility that operates specifically to provide surgical services to patients who do not require hospitalization. The expected duration of services should not exceed 24 hours after admission. An unexpected medical issue can sometimes require a longer stay, but CMS states that this should be rare.

See the CMS requirements for ambulatory surgery centers.

An ASC may operate independently or have a connection to a hospital system. A Medicare-certified, hospital-operated ASC must remain separately identified and enrolled from the hospital’s outpatient department.

How does an ASC differ from a hospital outpatient department?

Both settings can provide outpatient surgery, but they are not the same type of facility.

Setting	How it operates	When it may be appropriate
Ambulatory surgery center	A separate facility focused mainly on qualifying outpatient surgical procedures.	When the care team expects the patient to recover safely without hospital admission.
Hospital outpatient department	A department of a hospital that may provide surgery, imaging, observation, emergency support, and other outpatient services.	When the patient or procedure may require hospital-level resources, broader monitoring, or immediate access to additional services.

Your doctor may recommend one setting over another based on:

• Your overall health.
• The type and complexity of the procedure.
• The anesthesia or sedation you need.
• How long the procedure may take.
• Your expected recovery.
• Whether you may need hospital-level monitoring.
• The resources available at the facility.

The least expensive setting is not automatically the right one. Your medical needs and your care team’s judgment should guide the decision.

What procedures can an ASC perform?

The procedures available depend on the center’s license, equipment, clinical staff, specialties, and payer agreements.

Depending on the facility, an ASC may perform procedures involving:

• Gastroenterology and endoscopy.
• Eye care.
• Orthopedics.
• Pain management.
• Ear, nose, and throat care.
• Urology.
• Gynecology.
• General surgery.
• Podiatry.
• Dental or oral surgery.

Medicare maintains a covered procedure list and updates its ASC payment system over time. See the CMS ASC payment and covered-procedure resources.

Not every patient who needs an outpatient procedure is a suitable candidate for an ASC.

How does your care team decide whether an ASC is appropriate?

Your surgeon and anesthesia team review whether you can safely have the procedure and recover without hospital admission.

They may consider:

• Your current health.
• Your medical history.
• Heart or lung conditions.
• Diabetes and other chronic conditions.
• Your medications and supplements.
• Medication and food allergies.
• Previous problems with anesthesia.
• The expected length and complexity of the procedure.
• The type of anesthesia or sedation.
• Your ability to recover safely at home.
• Whether a responsible adult can help you after discharge.

Tell the clinical team about all your conditions and medications, even when they do not seem related to the planned procedure. Complete information helps the team decide whether the ASC has the right resources for your care.

ASC patient journey

What happens before, during, and after outpatient surgery

The exact process varies by procedure and facility, but most ASC visits follow these stages.

1. 1Confirm the facility

   Ask why the ASC is appropriate and confirm its license, quality information, and hospital transfer plan.

2. 2Verify insurance

   Check the network, prior authorization, deductible, estimated cost, and separate professional charges.

3. 3Prepare for surgery

   Follow medication and fasting instructions, report health changes, and arrange transportation.

4. 4Complete the procedure

   The team confirms your identity, procedure, surgical site, consent, allergies, and anesthesia plan.

5. 5Recover and go home

   Staff monitor your recovery and provide written instructions for medications, activity, and follow-up care.

Plan ahead: Many centers require a responsible adult to drive you home after sedation or anesthesia.

What should you check before choosing an ASC?

Ask whether the center is licensed in your state and whether it participates in Medicare when Medicare coverage applies.

Ask the ASC the following questions:

1. Is the center in-network with my exact insurance plan?
2. Is my surgeon credentialed to perform this procedure here?
3. Who will provide the anesthesia?
4. Is the anesthesia group in-network?
5. What happens if I need hospital care?
6. Which hospital accepts transfers from this center?
7. Who should I contact after regular business hours?
8. Where can I review the center’s quality information?

CMS collects and publicly reports selected facility-level quality information through the ASC Quality Reporting Program. The measures can address outcomes, patient safety, care processes, and coordination.

Use the CMS ambulatory surgery center quality data as one part of your research. No single measure gives a complete picture of a facility.

Verify your insurance before surgery

Contact both the ASC and your insurance plan before the procedure. Confirm that your policy will be active on the date of service and that your plan covers the procedure at that specific facility.

Ask the following questions:

• Is the ASC in-network with my plan?
• Is my surgeon in-network?
• Is the anesthesia provider or group in-network?
• Does the procedure require prior authorization?
• Do I need a referral from my primary care provider?
• How much of my deductible remains?
• What copayment or coinsurance may apply?
• What does the ASC facility fee include?
• Will implants or medical devices add to the cost?
• Will laboratory or pathology services be billed separately?
• Could I receive separate bills from other professionals?

Write down the date of each call, the representative’s name, and any reference number you receive. Keep that information with your estimate and authorization documents.

Insurance verification and prior authorization do not guarantee claim payment. The insurer makes its final decision after reviewing the procedure, claim codes, medical records, authorization, provider, facility, and plan rules.

Healthcare organizations can reduce authorization-related delays by checking requirements early and making sure the approved procedure, provider, facility, dates, and units match the planned service. See RCMGen’s prior authorization services for U.S. healthcare organizations.

Why might you receive more than one bill?

An outpatient procedure can involve several healthcare professionals and organizations.

You may receive a bill from:

• The ASC for the operating room, supplies, recovery area, and facility services.
• Your surgeon or procedural physician.
• The anesthesia professional or anesthesia group.
• A laboratory.
• A pathologist.
• A radiologist.
• An assistant surgeon.
• A medical-device or implant supplier.

Ask the center for a written estimate and a list of services that the facility estimate does not include.

Your final bill can differ from the estimate when:

• The procedure changes.
• You receive additional services.
• Another professional becomes involved.
• An implant or medical device is needed.
• Your deductible changes before claim processing.
• Your insurer processes the claim differently than expected.

How does Medicare cover ASC procedures?

Medicare Part B may cover approved outpatient surgical services at Medicare-participating ASCs when the service meets Medicare’s requirements.

After you meet the Part B deductible, you generally pay 20% of the Medicare-approved amount for covered provider services. Other costs may apply based on the procedure, facility, additional services, and other insurance. :contentReference[oaicite:6]{index=6}

Use the Medicare Procedure Price Lookup to compare available national average costs for selected procedures in ASCs and hospital outpatient departments.

The figures are estimates. Your actual cost can vary by location, procedure, insurance coverage, and the professionals involved.

If you have Medicare Advantage, contact your plan directly. Its network, prior authorization, and cost-sharing requirements may differ from Original Medicare.

Know your surprise-billing rights

The federal No Surprises Act protects many patients with private health insurance from certain unexpected out-of-network bills.

The protections may apply when an out-of-network professional provides nonemergency care during a visit to an in-network ASC. In a protected situation, your cost-sharing should generally be based on the in-network amount.

The protections might not apply when:

• The ASC itself is out-of-network.
• Your insurance type is not covered by the federal law.
• A state law applies differently.
• You sign a valid notice and consent form in a situation where the law permits consent.

Read every notice carefully. A notice and consent form may ask you to give up some balance-billing protections and accept higher out-of-network charges.

See the CMS guide to surprise-billing rights when using insurance.

What information should you provide before surgery?

The center needs accurate personal, insurance, and medical information to prepare for your procedure.

Identification and insurance information

Be ready to provide:

• Your full legal name.
• Your date of birth.
• Your current address and phone number.
• A government-issued photo ID.
• The front and back of your current insurance card.
• Primary and secondary insurance information.
• The policyholder’s information.
• Referral or prior authorization details.
• Workers’ compensation or auto-insurance information when the procedure relates to an accident.

Medical information

Provide a complete list of:

• Prescription medications.
• Over-the-counter medications.
• Vitamins and supplements.
• Medication, food, and latex allergies.
• Previous surgeries.
• Current medical conditions.
• Previous anesthesia problems.
• Recent illnesses or infections.
• Pregnancy or possible pregnancy, when relevant.
• Implanted devices, such as pacemakers, pumps, or stimulators.

Do not stop or change a prescription medication unless your surgeon, prescribing clinician, or anesthesia team gives you specific instructions.

Prepare for ASC surgery

The center will give you instructions based on your procedure and anesthesia plan. Read them early instead of waiting until the night before surgery.

Review your medications

Ask which medications you should:

• Continue as usual.
• Take with a small amount of water.
• Pause temporarily.
• Adjust before surgery.

Medication instructions are especially important for blood thinners, diabetes medicines, weight-management medicines, and drugs that affect stomach emptying.

Follow the fasting instructions

Confirm when you must stop eating and drinking. Do not assume that every procedure follows the same fasting rules.

Contact the center if you eat or drink after the cutoff time. The clinical team will decide whether the procedure can continue safely.

Report changes in your health

Call the center if you develop:

• A fever.
• A cough.
• Breathing problems.
• An infection.
• Vomiting or diarrhea.
• A new rash.
• Chest pain.
• Another significant change in your health.

Arrange transportation and support

Most surgery centers require a responsible adult to drive you home after sedation or anesthesia. Some centers also ask that someone stay with you during the first part of your recovery.

The center may postpone the procedure when you do not have safe transportation.

AHRQ advises patients to review medication instructions, follow fasting directions, bring an updated medication and allergy list, and ask questions when any preparation instruction is unclear. See the AHRQ ambulatory surgery preparation guide.

Prepare your home

Before the procedure:

• Fill prescriptions when possible.
• Buy dressings or supplies recommended by the care team.
• Prepare simple meals.
• Arrange help with children, pets, or household responsibilities.
• Move frequently used items within easy reach.
• Prepare a safe place to rest.

What happens when you arrive?

At check-in, staff may confirm:

• Your name and date of birth.
• The planned procedure.
• Your surgeon.
• The surgical site.
• Your insurance information.
• Your medications and allergies.
• Your transportation plan.
• Your consent forms.

Staff may ask the same questions more than once. Repeating these checks lets different members of the care team confirm that the information matches.

What happens before the procedure?

A nurse will usually check your vital signs and review your medical history. Your surgeon and anesthesia professional may speak with you before you enter the procedure room.

Before signing the consent form, make sure you understand:

• The procedure the surgeon plans to perform.
• Why the doctor recommends it.
• The expected benefits.
• Important risks.
• Reasonable alternatives.
• What may happen if you wait or decline the procedure.
• What recovery may involve.

Ask questions about anything you do not understand. You should feel comfortable with the information before you provide consent.

AHRQ’s ASC safety checklist includes confirmation of the patient’s identity, surgical procedure, surgical site, consent, allergies, anesthesia plan, equipment, implants, and recovery concerns. See the AHRQ ambulatory surgery checklist.

What happens after surgery?

After the procedure, the care team will move you to a recovery area.

Staff may monitor:

• Your breathing.
• Your blood pressure.
• Your heart rate.
• Your alertness.
• Your pain.
• Your nausea.
• The surgical site.
• Your recovery from anesthesia.

You should receive written discharge instructions before leaving. The instructions may explain:

• How to care for the surgical area.
• Which medications to take.
• Which activities to avoid.
• When you can shower.
• When you may eat and drink normally.
• When you may drive.
• When you may return to work.
• When you need follow-up care.
• Which symptoms require a call to the surgeon.
• Which symptoms require emergency care.
• Who to contact after regular office hours.

Do not rely only on your memory. Ask your support person to listen to the instructions and keep a copy of the paperwork.

What happens if you need hospital care?

An ASC is intended for patients who are not expected to need hospitalization. However, unexpected complications can occur.

The team may arrange a hospital transfer if you need:

• Longer monitoring.
• Advanced testing or imaging.
• Respiratory support.
• Blood products.
• Additional surgery.
• Inpatient treatment.
• A service the ASC cannot provide.

Ask which hospital the ASC uses for transfers and how the center will update your family.

What rights do you have at an ASC?

Medicare-certified ASCs must meet federal conditions that cover patient rights, infection control, medical records, admission, assessment, discharge, and facility management.

You should receive information about your right to:

• Participate in decisions about your treatment.
• Have your medical information kept private.
• Receive clear information before consenting to treatment.
• Create advance directives.
• Raise a concern or file a grievance.
• Receive information about physician ownership or financial interests in the facility.
• Receive clear discharge and follow-up instructions.

Ask for an interpreter, large-print information, or another communication accommodation when you need one.

See the CMS conditions for ASC coverage and patient rights.

Questions to ask before an ASC procedure

Frequently asked questions