Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum Sole proprietor
Steven Scott Mccallister, MD
Infectious Disease Physician in Watertown, MA · enumerated 2008.
Data current as of Jul 13, 2026 · sourced from CMS NPPES
National Provider Identifier
1114189651
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Registry record
Street address withheld: NPPES sole-proprietor addresses can be home addresses. See our data policy.
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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.
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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2008-06-26.