Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

Dr. Patrick Shawn Twomey, M.D.

Internal Medicine Physician in South San Francisco, CA · enumerated 2007 · practices at Arun Villivalam, MD., Inc..

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

National Provider Identifier

1265639454

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Registry record

Entity type Individual (Type 1)

Name Dr. Patrick Shawn Twomey

Credential M.D.

Sex Male

Practice address 1 Dna Way, South San Francisco, CA, 94080

Phone (650) 225-2580

Fax (650) 225-6000

Enumeration date Jun 29, 2007

Last updated in NPPES Feb 15, 2018

Taxonomy & licenses

207R00000X Internal Medicine Physician Allopathic & Osteopathic Physicians · License 0101245204 (VA) Primary

MD · Doctor of Medicine: A physician who completed medical school (allopathic medicine), residency training, and state licensure. About the MD 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.

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Frequently asked questions

How do I verify Patrick Twomey's NPI record?

Cross-check NPI 1265639454 against the official CMS registry at npiregistry.cms.hhs.gov. This page mirrors the same public NPPES data with a monthly snapshot.

Is NPI 1265639454 active?

Yes, as of the latest NPPES snapshot, NPI 1265639454 is active (record last updated 2018-02-15).

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2018-02-15.