What is an NPI number? A plain-English guide
An NPI is the 10-digit National Provider Identifier every US healthcare provider uses on claims. Here's what it is, who needs one, how to read it, and how to look one up.
An NPI — National Provider Identifier — is a unique 10-digit number that identifies a healthcare provider in the United States. It was created under HIPAA and is issued by the Centers for Medicare & Medicaid Services (CMS) through the National Plan and Provider Enumeration System (NPPES). If a provider or organization bills insurance, they have an NPI.
Who needs an NPI?
Two kinds of entities get NPIs, and the number itself tells you which:
- Type 1 (NPI-1) — individual providers: physicians, nurses, dentists, therapists, and other clinicians.
- Type 2 (NPI-2) — organizations: hospitals, group practices, clinics, pharmacies, labs, and supplier companies.
A single clinician can be associated with several organizations, so you'll often see one Type 1 NPI billing under different Type 2 NPIs.
How to read an NPI
An NPI is always exactly 10 digits and always starts with a 1 or a 2. The last digit is a check digit computed with the Luhn algorithm over the other nine digits (prefixed with the constant 80840). That means you can tell whether a number is even structurally valid before you ever look it up — a quick sanity check that catches transposed digits on a claim.
Patientary validates an NPI's check digit instantly, then confirms it against the live NPPES registry — so you know both that the number is well-formed and that it belongs to a real, active provider.
What information is attached to an NPI?
The NPPES registry is public. For any NPI you can see the provider's name, whether they're an individual or organization, their enumeration date and status, their taxonomy (specialty) codes, and their practice and mailing addresses. It does not include private clinical or patient data — it's a directory of who providers are, not what they do.
How to look up an NPI
You can search NPPES directly, but the official site is clunky. Patientary gives you the same live data in a clean interface — search by NPI number, provider name, organization, specialty or location — and, for developers and AI agents, the exact same lookup as a one-line API or MCP call.
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Open the NPI lookupFor developers and agents
Building software that touches claims, eligibility or provider directories? You'll need to resolve and validate NPIs constantly. Patientary's API returns a normalized provider record from the live registry, and validate endpoints check NPIs (and ICD-10 codes) in a single batched call before you submit.
Anything cited above is general reference, not medical, coding or billing advice. To look something up against live data, run a free NPI lookup, or search the ICD-10-CM code set.
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