Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

Mr. Daniel O'Brien, M.D.

Transplant Surgery Physician in Milwaukee, WI · enumerated 2015.

Data current as of Jul 13, 2026 · sourced from CMS NPPES

National Provider Identifier

1548659980

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Registry record

Entity type Individual (Type 1)

Name Mr. Daniel O'Brien

Credential M.D.

Sex Male

Practice address 2900 W Oklahoma Ave, Milwaukee, WI, 53215

Phone (414) 649-6000

Enumeration date Jan 22, 2015

Last updated in NPPES Oct 19, 2023

Taxonomy & licenses

204F00000X Transplant Surgery Physician Allopathic & Osteopathic Physicians · License A173264 (CA) Secondary

208600000X Surgery Physician Allopathic & Osteopathic Physicians · License A173264 (CA) Secondary

208600000X Surgery Physician Allopathic & Osteopathic Physicians · License 036-165946 (IL) Secondary

390200000X Student in an Organized Health Care Education/Training Program Student, Health Care · License 11018992A (IN) Secondary

204F00000X Transplant Surgery Physician Allopathic & Osteopathic Physicians · License 82286 (WI) Primary

MD · Doctor of Medicine: A physician who completed medical school (allopathic medicine), residency training, and state licensure. About the MD credential

Other identifiers

Identifier	Type	State	Issuer
100246297	Medicaid	WI	-

What is an NPI number?

A National Provider Identifier (NPI) is a unique 10-digit number that CMS assigns to every U.S. healthcare provider and organization under HIPAA. Type 1 NPIs identify individual providers; Type 2 NPIs identify organizations. The NPI appears on insurance claims, prescriptions, and credentialing paperwork, and never changes, even if the provider moves or changes specialty.

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Frequently asked questions

What specialty is Daniel O'Brien?

Daniel O'Brien is registered in NPPES with the primary taxonomy of Transplant Surgery Physician. The taxonomy code describes the provider's classification and area of specialization for claims and credentialing.

Is this the official NPI registry?

No. NPI Portal is a private site built on public CMS NPPES data. The official registry is npiregistry.cms.hhs.gov, operated by CMS.

Other providers at this practice address

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2023-10-19.