Type 2 · Organization ✓ Active NPI ✓ Valid NPI checksum

Mathias Masem, M.D.

Q: What type of organization is Mathias Masem, M.D.?

Mathias Masem, M.D. is registered in NPPES as a Specialist (its primary provider taxonomy).

Specialist in Oakland, CA · enumerated 2006 · authorized official Mathias Masem, Sole Practioner.

Data current as of Jul 11, 2026 · sourced from CMS NPPES

National Provider Identifier

1457371643

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Registry record

Entity type Organization (Type 2)

Legal business name Mathias Masem, M.D.

Practice address 80 Grand Ave.,, Suite 600, Oakland, CA, 94612

Phone (510) 763-0709

Fax (510) 763-8753

Enumeration date Jul 20, 2006

Last updated in NPPES Aug 22, 2020

Taxonomy & classification

174400000X Specialist Other Service Providers · License G34134 (CA) Primary

Authorized official

Name Mathias Masem

Title Sole Practioner

Phone (510) 763-0709

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 type of organization is Mathias Masem, M.D.?

Mathias Masem, M.D. is registered in NPPES as a Specialist (its primary provider taxonomy).

What is a Type 2 NPI?

A Type 2 NPI identifies an organization (group practice, hospital, pharmacy, lab), while Type 1 NPIs identify individual providers. Organizations bill under their Type 2 NPI.

Source: CMS NPPES (public data). Snapshot 2026-07-11. Provider record last updated 2020-08-22.