Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum
William A Ernstein, O.D.
Optometrist in Palatine, IL · enumerated 2006.
Data current as of Jul 13, 2026 · sourced from CMS NPPES
National Provider Identifier
1427133420
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Registry record
Entity type Individual (Type 1)
Name William A Ernstein
Credential O.D.
Sex Male
Practice address 251 E Northwest Hwy, Palatine, IL, 60067
Phone (847) 358-4950
Fax (847) 358-4990
Enumeration date Oct 26, 2006
Last updated in NPPES Jul 8, 2007
Taxonomy & licenses
OD · Doctor of Optometry: A licensed optometrist providing primary vision care, eye exams, and corrective lenses.
About the OD 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.
Frequently asked questions
What is the NPI number for William Ernstein?
The National Provider Identifier (NPI) for William Ernstein is 1427133420, a Type 1 (individual) record in the CMS NPPES registry.
Where does William Ernstein practice?
The practice location on file with NPPES is in Palatine, IL. Providers can have multiple locations; NPPES lists the primary practice address.
Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2007-07-08.