The Inpatient Only List: How Medicare Pays for Your Surgery

The difference between Part A and Part B coverage will cost you

Surgery doesn’t come cheap, and you will want to know how (or if) Medicare is going to pay for it long before you go under the knife.

Some surgeries will automatically be covered by Medicare Part A but others will be covered by Medicare Part B. The difference could add up to thousands more in out-of-pocket expenses.

Wife sitting next to husband who is in hospital bed waiting for inpatient surgery

JodiJacobson / Getty Images

Preparing for Surgery

There are several things you need to think about before having surgery. The first, of course, is whether or not the procedure is necessary or if there are other treatment alternatives.

After that come the logistics of how and where your surgery will be performed, and how much insurance will pay toward the bill. You should not undergo any elective surgery or procedure without addressing these issues beforehand.

Few people are aware that the Centers for Medicare & Medicaid Services (CMS) has established a list of surgeries that will be covered by Medicare Part A.

Other surgeries, as long as there are no complications and the person undergoing surgery does not have significant chronic conditions that put them at high risk for complications, default to Medicare Part B. This affects not only how much you will pay, but where your surgery can be performed.

Medicare’s Inpatient Only Surgery List

Every year, CMS releases an updated Inpatient Only (IPO) surgery list. The surgeries on this list are not arbitrarily selected.

These procedures tend to be more complex and have a higher risk for complications. They are also likely to need post-operative monitoring overnight and often have a long recovery time. CMS understands that these surgeries require a high level of care and that these patients are unlikely to go home the same day or even the day after surgery.

Examples of Inpatient Only surgeries include:

You may be surprised to learn that very few spinal procedures are on the list. In fact, most types of spinal fusions and discectomies are not on the Inpatient Only list.

Other common procedures were once on the list, but have since been removed. As of 2018, total knee replacement (total knee arthroplasty) is no longer automatically covered by Part A. Total hip replacement was taken off the list in 2020. Both are now considered Part B procedures.

Changes to the IOL in 2022

Back in 2020, CMS announced that the Inpatient Only list would be phased out over three years. The first group of surgeries – 298 musculoskeletal and spinal procedures – were removed from the list in 2021. However, due to concerns from surgeons and medical facilities, CMS has put all but three of those surgeries back on the IPO list as of January 1, 2022.

Surgeries Performed in a Hospital

For the safety of Medicare beneficiaries, Inpatient Only surgeries must be performed in a hospital. Medicare Part A covers the majority of surgical costs, and you will pay a deductible of $1,600 in 2023 in addition to 20% of doctor fees for your hospital stay.

That does not mean that other surgeries can’t be performed in a hospital setting. If a surgery is not on the Inpatient Only list and not on Addendum AA (see Ambulatory Surgery Centers below), it must be performed in a hospital.

These surgeries will be covered by Medicare Part B. In that case, you will be required to pay a 20% coinsurance for your surgery and all aspects of your care from anesthesia to medications to medical supplies to your hospital bed. When it is all added together, it is easy to see you would spend far more than the Part A deductible amount.

The Two Midnight Rule

It is possible that you could have a surgery that is not on the Inpatient Only list and still have your hospital stay covered by Medicare Part A. This could happen if your hospital stay is expected to (or already has) crossed two midnights and you still have care that Medicare considers to be medically necessary.

Surgeries Performed in Ambulatory Surgery Centers

Surgeries on the Inpatient Only list cannot be performed in an ambulatory surgery center (ASC). In fact, CMS publishes a specific list of outpatient surgeries that can be performed at an ASC. This list is referred to as Addendum AA.

By definition, an ASC is an outpatient medical facility where surgeries are performed. It may or may not be affiliated with a hospital. You may also hear ASCs referred to as same-day surgery centers.

According to CMS guidelines, “The surgical codes that are included on the ASC list of covered surgical procedures are those that have been determined to pose no significant safety risk to Medicare beneficiaries when furnished in ASCs and that are not expected to require active medical monitoring at midnight of the day on which the surgical procedure is performed (overnight stay).”

Simply put, these surgeries are low risk and are not expected to require care and monitoring beyond 24 hours.

Examples of procedures that can be performed in ACS include:

These surgeries will be covered by Medicare Part B at a coinsurance of 20% for each service.

CMS Surgery Lists and Patient Safety

The Inpatient Only surgery list is not only about payment; it is also about safety.

Staffing in a hospital is very different than that in an ASC. Whereas a hospital has 24-hour resources, an ASC may have reduced staff overnight. Most ASCs will not have a physician onsite after hours.

If there is a complication after hours, it is unlikely that an ASC would have the proper resources and personnel available to manage it. This may necessitate transferring a patient to a nearby hospital.

Since care in an ASC is limited to a 24-hour stay, if a patient required more time for recovery, the patient would also need to be transferred to a hospital.

For these reasons, all procedures on the Inpatient Only list must be performed in a hospital.

Comparing Traditional Medicare to Medicare Advantage

Traditional Medicare (Part A and Part B) and Medicare Advantage (Part C) follow different rules. While traditional Medicare follows all the payment guidelines described above, Medicare Advantage plans do not have to. They can choose to pay for surgeries as inpatient or outpatient—that is, pay more or less—regardless of their being on the Inpatient Only list.

Inpatient vs. Outpatient

Medicare Advantage plans cover everything that Original Medicare does. Many people then ask how they can then cover Inpatient Only Surgeries as outpatient procedures. The reason is that inpatient and outpatient are not services per se. They are payment designations. As long as Medicare Advantage plans provide coverage for the surgery, regardless of the payment designation, they are in adherence with the law. This was addressed in the court case Alexander vs. Azar.

Medicare Advantage plans often turn to national guidelines such as MCG Health's Care Guidelines® or McKesson Health Solutions' Interqual™ to determine whether a surgery is inpatient appropriate. Insurance companies may also have internal processes that determine how they will cover different surgeries.

Regardless of the type of Medicare plan you have, a surgery on the Inpatient Only list must be performed in a hospital.​

There could be advantages to having a Medicare Advantage plan. Consider rehabilitation care after your surgery. In order for traditional Medicare to pay for a stay in a skilled nursing facility, you need to have been admitted for at least three consecutive days as an inpatient.

Medicare Advantage plans have the option of waiving the three-day rule. This could save you considerably in rehabilitation costs if your hospital stay is shorter than that.


Medicare does not treat all surgeries the same. An Inpatient Only surgery list is released every year by CMS. These procedures are automatically approved for Part A coverage and must be performed in a hospital. All other surgeries, as long as there are no complications, are covered by Part B.

CMS also releases an annual Addendum AA that specifies what outpatient (i.e., not Inpatient Only) procedures can be performed in ambulatory surgery centers. All remaining outpatient surgeries must be performed in a hospital for anyone on Medicare.

A Word from VeryWell

Not all surgeries are covered by Medicare Part A even when you stay overnight in a hospital. That could affect how much you will pay out of pocket. Find out what part of Medicare your procedure falls under ahead of time so that you can better plan for it and avoid additional stress.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Medicare & Medicaid Services. FY 2022 IPPS final rule home page.

  2. Centers for Medicare & Medicaid Services. CY 2022 Medicare Hospital Outpatient Prospective Payment System and Ambulatory Surgical Center Payment System Final Rule (CMS-1753FC).

  3. Centers for Medicare & Medicaid Services. 2023 Medicare Parts A & B Premiums and Deductibles 2023 Medicare Part D Income-Related Monthly Adjustment Amounts.

  4. Centers for Medicare & Medicaid Services. Addendum AA, BB, DD1, DD2 and EE.

  5. Centers for Medicare & Medicaid Services. Medicare claims processing manual. Chapter 14 - ambulatory surgical centers.

  6. Alexander v. Azar, No. 3:11-cv-1703 (MPS) (D. Conn. Mar. 24, 2020)

By Tanya Feke, MD
Tanya Feke, MD, is a board-certified family physician, patient advocate and best-selling author of "Medicare Essentials: A Physician Insider Explains the Fine Print."