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

Dr. John Brian Westerdahl, PHD, MPH, RDN

Registered Dietitian in Simi Valley, CA · enumerated 2024.

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

National Provider Identifier

1518784859

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Registry record

Entity type Individual (Type 1)

Name Dr. John Brian Westerdahl

Credential PHD, MPH, RDN

Sex Male

Practice address Simi Valley, CA, 93065

Phone (805) 722-7958

Enumeration date Sep 25, 2024

Last updated in NPPES Sep 25, 2024

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

Taxonomy & licenses

133V00000X Registered Dietitian Dietary & Nutritional Service Providers · License 625522 (CA) Primary

PHD · Doctor of Philosophy: A doctoral degree; in healthcare often held by clinical psychologists and researchers. About the PHD credential

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

Is NPI 1518784859 active?

Yes, as of the latest NPPES snapshot, NPI 1518784859 is active (record last updated 2024-09-25).

How do I verify John Westerdahl's NPI record?

Cross-check NPI 1518784859 against the official CMS registry at npiregistry.cms.hhs.gov. This page mirrors the same public NPPES data with a monthly snapshot.

Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2024-09-25.