NPI Portal NPI Lookup & Verification

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

Diem-Tran Isabelle Nguyen, MD

Allergy & Immunology Physician in Orange, CA · enumerated 2019.

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

National Provider Identifier

1215498761

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Registry record

Entity type Individual (Type 1)
Name Diem-Tran Isabelle Nguyen
Credential MD
Sex Female
Practice address Orange, CA, 92868
Phone (714) 633-6363
Fax (714) 633-0178
Enumeration date Mar 27, 2019
Last updated in NPPES Jun 24, 2024

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

Taxonomy & licenses

207K00000X Allergy & Immunology Physician Allopathic & Osteopathic Physicians · License A194587 (CA) 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.

Read the full guide → Validate an NPI →

Frequently asked questions

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.
What specialty is Diem-Tran Nguyen?
Diem-Tran Nguyen is registered in NPPES with the primary taxonomy of Allergy & Immunology Physician. The taxonomy code describes the provider's classification and area of specialization for claims and credentialing.

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2024-06-24.