Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

Dr. Karthikeyan Viswanathan, DO

Internal Medicine Physician in Los Altos, CA · enumerated 2015.

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

National Provider Identifier

1396128336

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Registry record

Entity type Individual (Type 1)

Name Dr. Karthikeyan Viswanathan

Credential DO

Sex Male

Practice address 4546 El Camino Real Ste B7, Los Altos, CA, 94022

Phone (866) 362-4246

Fax (650) 260-6030

Enumeration date Jul 8, 2015

Last updated in NPPES Aug 21, 2025

Taxonomy & licenses

207R00000X Internal Medicine Physician Allopathic & Osteopathic Physicians · License 20A19044 (CA) Primary

DO · Doctor of Osteopathic Medicine: A fully licensed physician trained in osteopathic medical schools, with the same practice rights as an MD. About the DO 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

What is the NPI number for Karthikeyan Viswanathan?

The National Provider Identifier (NPI) for Karthikeyan Viswanathan is 1396128336, a Type 1 (individual) record in the CMS NPPES registry.

Where does Karthikeyan Viswanathan practice?

The practice location on file with NPPES is in Los Altos, CA. Providers can have multiple locations; NPPES lists the primary practice address.

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2025-08-21.