Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

Allan O Diefendorf, PH.D.

Audiologist in Indianapolis, IN · enumerated 2009.

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

National Provider Identifier

1447484464

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Registry record

Entity type Individual (Type 1)

Name Allan O Diefendorf

Credential PH.D.

Sex Male

Practice address 702 Barnhill Dr, Suite 0860, Indianapolis, IN, 46202

Phone (317) 630-8970

Fax (317) 630-8958

Enumeration date May 5, 2009

Last updated in NPPES Jan 29, 2014

Taxonomy & licenses

231H00000X Audiologist Speech, Language and Hearing Service Providers · License 23001934 (IN) Primary

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

Other identifiers

Identifier	Type	State	Issuer
23001934	Other	IN	0000000000

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 Allan Diefendorf?

Allan Diefendorf is registered in NPPES with the primary taxonomy of Audiologist. 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 2014-01-29.