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Home > Glossary > ancillary services

ancillary services

What are ancillary services?

medicareresources.org Glossary

What are ancillary services?

Ancillary services are medical services provided in a hospital while a patient is admitted, but which can be paid by Medicare Part B (outpatient care). This can happen when the Part A (inpatient) claim is denied because Medicare believes that it was unreasonable or unnecessary for the person to be admitted as an inpatient.1 Ancillary services include care such as diagnostic x-rays and lab tests, prosthetic devices, physical therapy, and various screening tests, among others.2

In 2013, CMS finalized regulations to make it easier for hospitals to rebill services to Medicare Part B if a claim to Medicare Part A is denied.3 So instead of just being able to obtain payment for the limited list of ancillary services that were previously eligible for Part B coverage in that situation, hospitals can now rebill most services under Part B if the Part A claim is denied.

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How will my costs be affected by inpatient or observation status?

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If you aren't actually admitted to a hospital – and are classified as "under observation" – your costs could change significantly.

inpatient care

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Inpatient care is medical treatment administered to a patient whose condition requires treatment in a hospital or other health care facility, and the patient is formally admitted to the facility by a doctor.

Medicare Part A ‘hospital insurance’ – coverage of inpatient care

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Footnotes

  1. ”Inpatient Ancillary Services” Noridian Medicare. And “Medicare Benefit Policy Manual,  Chapter 6 – Hospital Services Covered Under Part B, Section 10” Centers for Medicare & Medicaid Services. Accessed May 29, 2025 ⤶
  2. ”Medicare Benefit Policy Manual,  Chapter 6 – Hospital Services Covered Under Part B, Section 10” Centers for Medicare & Medicaid Services. Accessed May 29, 2025 ⤶
  3. ”CMS finalizes FY 2014 policy and payment changes for inpatient stays in acute-care and long-term care hospitals” Centers for Medicare & Medicaid Services. Aug. 2, 2013 ⤶