Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

William M Klein, MD

Internal Medicine Physician in Great Neck, NY · enumerated 2006.

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

National Provider Identifier

1659359578

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Registry record

Entity type Individual (Type 1)

Name William M Klein

Credential MD

Sex Male

Practice address 1000 Northern Blvd, Suite 230, Great Neck, NY, 11021

Phone (516) 627-4433

Fax (516) 627-0552

Enumeration date Jan 3, 2006

Last updated in NPPES May 3, 2011

Taxonomy & licenses

207R00000X Internal Medicine Physician Allopathic & Osteopathic Physicians · License 205508 (NY) 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
136958	Other	-	VYTRA
3651757	Other	-	CIGNA
A28929	Other	-	1199
WK07R53510	Other	NY	BLUE SHIELD
P3695174	Other	-	OXFORD
205508	Other	-	HIP
4C4799	Other	-	HEALTHNET
2594094	Other	-	GHI

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

What specialty is William Klein?

William Klein is registered in NPPES with the primary taxonomy of Internal Medicine 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 2011-05-03.