Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

John O Thayer Jr., MD

Thoracic Surgery (Cardiothoracic Vascular Surgery) Physician in Hartford, CT · enumerated 2005.

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

National Provider Identifier

1942293956

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Registry record

Entity type Individual (Type 1)

Name John O Thayer Jr.

Credential MD

Sex Male

Practice address 1000 Asylum Ave, Ste 3201a, Hartford, CT, 06105

Phone (860) 714-1094

Fax (860) 714-8850

Enumeration date Aug 24, 2005

Last updated in NPPES Mar 30, 2009

Taxonomy & licenses

208G00000X Thoracic Surgery (Cardiothoracic Vascular Surgery) Physician Allopathic & Osteopathic Physicians · License 028081 (CT) 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
001280817	Medicaid	CT	-

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 John Thayer?

John Thayer is registered in NPPES with the primary taxonomy of Thoracic Surgery (Cardiothoracic Vascular 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 2009-03-30.