Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

Margaret A O'Brien, R.D.

Registered Dietitian in Phoenix, AZ · enumerated 2006.

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

National Provider Identifier

1659331536

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Registry record

Entity type Individual (Type 1)

Name Margaret A O'Brien

Credential R.D.

Sex Female

Practice address 1441 N 12th St Fl 2, Phoenix, AZ, 85006

Phone (602) 521-5200

Fax (602) 521-5201

Enumeration date Mar 24, 2006

Last updated in NPPES Nov 8, 2018

Taxonomy & licenses

133V00000X Registered Dietitian Dietary & Nutritional Service Providers · License 554938 (AZ) Primary

RD · Registered Dietitian: A nutrition professional credentialed by the Commission on Dietetic Registration. About the RD credential

Other identifiers

Identifier	Type	State	Issuer
796708	Medicaid	AZ	-

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 Margaret O'Brien?

Margaret O'Brien is registered in NPPES with the primary taxonomy of Registered Dietitian. 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 2018-11-08.