Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

William R. Mason, D.O.

Anesthesiology Physician in Wausau, WI · enumerated 2006.

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

National Provider Identifier

1942221791

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Registry record

Entity type Individual (Type 1)

Name William R. Mason

Credential D.O.

Sex Male

Practice address 425 Pine Ridge Blvd, Suite 211, Wausau, WI, 54401

Phone (715) 845-5505

Fax (715) 848-2884

Enumeration date Jul 21, 2006

Last updated in NPPES Jul 9, 2007

Taxonomy & licenses

207L00000X Anesthesiology Physician Allopathic & Osteopathic Physicians · License 30749020 (WI) Primary

DO · Doctor of Osteopathic Medicine: A fully licensed physician trained in osteopathic medical schools, with the same practice rights as an MD. About the DO credential

Other identifiers

Identifier	Type	State	Issuer
30046800	Medicaid	WI	-
27359	Other	WI	SECURITY HEALTH MEDICAID
27359	Other	WI	SHP
30046800	Other	WI	MANAGED HEALTH CARE
MASON	Other	WI	MASON

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

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.

What specialty is William Mason?

William Mason is registered in NPPES with the primary taxonomy of Anesthesiology Physician. The taxonomy code describes the provider's classification and area of specialization for claims and credentialing.

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2007-07-09.