Skip to content
FonteumPublic-records evidence
Screen 25 NPIs free →Buy $129 certificate →
Fonteum Data GlossaryProvider

UPIN: Definition and Healthcare Context

Full name: Unique Physician Identification Number

The Unique Physician Identification Number (UPIN) was a six-character alphanumeric Medicare identifier assigned to physicians beginning in 1984. UPINs were required on Medicare claims for referring and ordering physicians. CMS replaced UPINs with NPIs for all HIPAA-covered transactions on May 23, 2007. Although no longer used in active Medicare billing, UPINs appear in legacy Medicare claims data and historical research datasets, particularly for studies using data predating the NPI transition.

Source file
Not reported
Published
Not reported
Retrieved
Not reported
Snapshot
Not retained for this reference page
Data as of
Not reported
Last updated: 2026-07-11Reviewed by: Dr. Jennifer Montecillo, MD — Gullas College of Medicine, 2019. Non-practicing medical reviewer.

How it’s used

  • CMS PECOS Medicare Provider Enrollment: historical PECOS records reference UPIN-to-NPI crosswalk mappings maintained by CMS during the transition period.
  • CMS NPPES NPI Registry: CMS published UPIN-to-NPI crosswalk files when NPPES launched to support legacy system migration.

Frequently asked questions

What is a UPIN?
A UPIN (Unique Physician Identification Number) was a legacy Medicare identifier for physicians, replaced by the NPI in May 2007.
Is UPIN still used?
No. UPINs are no longer valid for Medicare billing. They are retired identifiers that appear only in historical claims data from before May 2007.
What replaced UPIN?
The NPI (National Provider Identifier) replaced the UPIN for all HIPAA-covered transactions as of May 23, 2007.

Related terms

Authoritative sources

← All glossary terms

What’s on file, by the numbers

Platform snapshot · 2026-08-12

13.4Mproviders & companiesProviders, organizations, owners, and facilities on file
26.2Msource-linked factsSource-linked field facts in the dated platform snapshot
90sources with dataDistinct snapshot source IDs with at least one positive record count
73fresh sourcesDistinct source IDs whose latest positive-data snapshot falls within the preceding 45 days
111sources integratedActive registry rows; integration does not establish a load
13state Medicaid jurisdictionsDistinct states represented in the state-exclusions serving table

Integrated, with-data, and fresh-observation counts are separate. No platform-wide source-completeness count is published. Completeness is source-specific and must be evaluated against the named source's expected scope. State coverage is a separate jurisdiction measure.

Source authority is record-specific

Use the issuer named on the record.

Fonteum spans federal, state, and global public publishers. A source page or returned record identifies its issuer and dataset where that metadata is available. A platform registry count does not assign every page to one authority or establish loaded, fresh, or complete coverage.

Browse source records and their stated limitations →

Reproducible by design

Inspect the evidence each published figure actually supplies.

Source and date

Research pages expose the named public file and observation date where those fields are available. Source-file SHA-256 coverage is separate; facts do not currently link deterministically to signatures.

Available derivation

Studies with a retained release and committed derivation link the SQL or method used. Other studies state the evidence and reproduction limits they actually have.

Daily observations

Dated table row-count observations can detect local drift. They do not imply that an upstream publisher released or Fonteum ingested new data that day.

Named medical review

Reviewed by Jennifer Montecillo, MD, medical reviewer. Non-practicing medical reviewer.

Read the full provenance and attestation methodology →

Request access