An ASC, or ambulatory surgery center, is a medical facility designed specifically for surgeries and procedures that don’t require an overnight hospital stay. Patients arrive, have their procedure, recover, and go home the same day, all within a maximum of 24 hours. As of 2023, there are 6,308 Medicare-certified ASCs operating across the United States, and the number is growing steadily, with 250 new centers opening that year alone.
How an ASC Works
An ambulatory surgery center operates exclusively for outpatient surgical services. Unlike a hospital, it doesn’t have inpatient beds or an emergency department. You check in, go through a pre-operative area, have your surgery performed in a fully equipped operating room, spend time in a recovery area until the medical team clears you, and leave the same day. The entire visit from admission to discharge must stay under 24 hours.
ASCs are staffed with surgeons, anesthesiologists, registered nurses, and surgical technicians. A registered nurse must be available for emergency treatment whenever a patient is in the facility. Each center has a governing body that takes legal responsibility for policies, grants surgical privileges to physicians, and maintains a quality improvement program that tracks outcomes over time.
To participate in Medicare, an ASC must be certified as meeting federal conditions for coverage, which span surgical safety, infection control, pharmaceutical handling, medical recordkeeping, and patient rights. Most ASCs also pursue accreditation from an outside organization like the Joint Commission or the Accreditation Association for Ambulatory Health Care. The Joint Commission is designated by Medicare as an approved accreditor, meaning its survey process can simultaneously certify a facility for Medicare participation.
Common Procedures Performed at ASCs
The procedures done at ASCs tend to be lower-risk surgeries that have predictable recovery times. The most common, ranked by volume, include:
- Cataract and lens procedures
- Muscle, tendon, and soft tissue surgeries
- Gallbladder removal
- Joint procedures (fusions, repairs, removal of damaged tissue)
- Hernia repairs (inguinal, femoral, umbilical, and incisional)
- Skin and breast procedures
- Knee cartilage removal
- Tonsil and adenoid removal
- Nerve decompression surgery
These are all procedures where the patient can safely recover at home rather than in a hospital bed. More complex operations, or those involving patients with serious underlying health conditions, are still routed to hospitals.
Who Is a Good Candidate
Before scheduling a procedure at an ASC, an anesthesiologist evaluates your overall health using a classification system developed by the American Society of Anesthesiologists. It ranges from ASA I (a healthy person with no medical conditions) to ASA IV (someone with severe, life-threatening conditions like advanced heart failure or severe lung disease requiring home oxygen).
ASCs generally treat patients who fall into the healthier categories. Research from Medicare data confirms that ASC patients, on average, are healthier and have fewer coexisting medical conditions than patients who undergo similar procedures in hospital outpatient departments. If you have well-controlled blood pressure or mild diabetes, you may still be a candidate. If you have multiple serious conditions that could complicate anesthesia or recovery, your surgeon will likely recommend a hospital setting instead.
How ASCs Differ From Hospitals
The most obvious difference is scope. A hospital outpatient department sits within a larger hospital campus, with immediate access to intensive care units, emergency services, and inpatient beds if something goes wrong. An ASC is a standalone facility (or a distinct, separately certified unit even if a hospital owns it) that handles only same-day surgery.
This narrower focus creates a different patient experience. ASCs typically offer shorter wait times, more flexible scheduling, and a streamlined process since every staff member and every room is oriented around outpatient procedures. You won’t be sharing space with emergency patients or navigating a sprawling hospital campus.
Ownership also differs. ASCs can be owned by physicians, by hospitals, or by a combination of both. When a hospital owns an ASC, the center still operates under a separate Medicare agreement and is paid at ASC rates, not hospital outpatient rates. It cannot simply convert to a hospital outpatient department.
Cost Differences
One of the biggest practical reasons ASCs exist is cost. The same procedure performed at an ASC costs significantly less than at a hospital outpatient department, both for insurers and for you as the patient.
A study comparing sports medicine procedures for Medicare recipients found that across 62 different procedure types, total costs were 40% lower at ASCs. Facility fees, which make up the largest chunk of the bill, were 45% lower. The savings passed directly to patients too: out-of-pocket costs were 37% lower on average. For shoulder procedures specifically, patients paid roughly $724 at an ASC compared to $1,252 at a hospital outpatient department. Hip procedures showed even larger gaps, with about 46% savings on total costs.
These differences exist largely because ASCs have lower overhead. They don’t maintain emergency departments, inpatient wards, or the extensive infrastructure a full hospital requires. That leaner operation translates into lower facility fees, which drive down both what insurance pays and what you owe.
Safety and Infection Rates
ASCs must meet the same core safety standards around infection control, medication management, and staff competency that apply to hospital-based surgical facilities. Infection rates in ambulatory settings have consistently been reported as lower than hospital rates. In orthopedic surgery, for example, the infection rate for clean procedures in hospitals ranges from 0.5% to 6.5%, while a comparable study at an orthopedic ASC found a rate as low as 0.33%.
Several factors likely contribute to this. ASCs handle a narrower range of procedures with a more predictable patient population. They don’t have the constant flow of critically ill or immunocompromised patients that hospitals do, which reduces the overall infectious risk in the environment. The facilities are also smaller, making it easier to maintain strict sterile protocols across every operating room.
Every ASC is required to run a quality assessment and performance improvement program that collects data on outcomes and uses it to identify problems. Accrediting bodies like the Joint Commission conduct on-site surveys that evaluate infection control practices, staff competency, patient assessment processes, and medication management as part of ongoing oversight.
Growth of ASCs in the U.S.
ASCs are the fastest-growing type of surgical facility participating in Medicare. The number of certified centers grew 2.5% from 2022 to 2023, reaching 6,308 facilities. That growth has been consistent, averaging about 2.2% annually from 2018 to 2022. In 2023 alone, 250 new ASCs opened while 95 closed or merged, producing a net gain of 155 centers.
This expansion reflects a broader shift in healthcare toward outpatient settings. Advances in surgical techniques, anesthesia, and pain management mean procedures that once required a hospital stay can now be done safely on an outpatient basis. Insurers and Medicare have financial incentives to steer appropriate cases toward ASCs, where the same procedure costs considerably less. For patients, the appeal is straightforward: lower bills, shorter visits, and a facility built entirely around getting you in, through surgery, and home the same day.