Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

William E. Probst, MD

Obstetrics & Gynecology Physician in Tracy, CA · enumerated 2006 · practices at Kaiser Foundation Health Plan Inc.

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

National Provider Identifier

1407934391

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Registry record

Entity type Individual (Type 1)

Name William E. Probst

Credential MD

Sex Male

Practice address 2185 W Grant Line Rd, Tracy, CA, 95377

Phone (209) 839-3200

Enumeration date Nov 1, 2006

Last updated in NPPES Dec 2, 2021

Taxonomy & licenses

207V00000X Obstetrics & Gynecology Physician Allopathic & Osteopathic Physicians · License G75094 (CA) 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
00G750940	Medicaid	CA	-

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 NPI 1407934391 active?

Yes, as of the latest NPPES snapshot, NPI 1407934391 is active (record last updated 2021-12-02).

How do I verify William Probst's NPI record?

Cross-check NPI 1407934391 against the official CMS registry at npiregistry.cms.hhs.gov. This page mirrors the same public NPPES data with a monthly snapshot.

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2021-12-02.