Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum Sole proprietor

Dr. Mathias A. Masem, M.D.

Orthopaedic Hand Surgery Physician in Oakland, CA · enumerated 2006.

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

National Provider Identifier

1508810938

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Registry record

Entity type Individual (Type 1)

Name Dr. Mathias A. Masem

Credential M.D.

Sex Male

Practice address Oakland, CA, 94612

Phone (510) 763-0884

Fax (510) 763-1574

Enumeration date May 20, 2006

Last updated in NPPES Dec 18, 2014

Street address withheld: NPPES sole-proprietor addresses can be home addresses. See our data policy.

Taxonomy & licenses

207X00000X Orthopaedic Surgery Physician Allopathic & Osteopathic Physicians · License G34134 (CA) Secondary

207XS0106X Orthopaedic Hand Surgery Physician Allopathic & Osteopathic Physicians · License G34134 (CA) 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
00G341340	Medicaid	CA	-

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.

Read the full guide → Validate an NPI →

Frequently asked questions

What specialty is Mathias Masem?

Mathias Masem is registered in NPPES with the primary taxonomy of Orthopaedic Hand 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.

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2014-12-18.