Methodology and sources
Data
| What | Source | Checked |
|---|---|---|
| Taxonomy codes, names, groups, definitions | NUCC Health Care Provider Taxonomy code set, version 26.1 (CSV) | 2026-10-24 |
| Taxonomy → Medicare specialty | CMS Medicare Provider and Supplier Taxonomy Crosswalk, August 2026 | 2026-10-24 |
| Medicare enrollment counts | CMS Medicare Fee-For-Service Public Provider Enrollment, extract of 2026-09-29 | 2026-10-24 |
| NPI lookup results | CMS NPI Registry API, queried live through this site's server; nothing is stored | live |
How the counts work
The enrollment file lists 2,634,090 enrollments for 2,576,755 unique NPIs. Counts on this site are unique NPIs per enrollment provider type, and per state for state figures — a provider enrolled in two states counts once in each state and once nationally. Specialty pages cover practitioner types (14-xx) with at least 300 NPIs; the "order and referring only" figure on each page is the matching 33-xx type. Territories are included in national totals but have no state page.
Crosswalk
Each taxonomy code's Medicare specialty comes from CMS's crosswalk, matched on the exact code. The count shown beside it is the national enrollment for the practitioner type with the same specialty code. Codes absent from the crosswalk are marked as such; that does not mean the provider cannot bill Medicare under another type.
The NPI lookup
Searches go from your browser to this site's Worker, which forwards a fixed set of fields to the CMS NPI Registry API and returns the answer (cached for an hour). The check-digit test runs in your browser using the Luhn formula with the 80840 prefix that CMS specifies for NPIs.
Which codes and groups get a page
Every one of the 883 codes is listed on the code index and its group page. 719 have a page of their own. The other 164 have no Medicare crosswalk, no related codes, no dated history in NUCC's notes and a one-line definition — nothing a separate page could add — so their full entry sits on the group page and their address redirects there. Groups with fewer than ten codes, or a single classification (whose classification page already lists every code), are listed on the code index only.
Left out, and why
- Counts of all NPIs by taxonomy: the NPPES bulk file was offline for maintenance when this site was built (October 2026); counts here are Medicare enrollments, not all NPIs.
- Individual provider pages: the registry is the place for those; this site aggregates and links to it.
- NUCC notes and board-certification references: summarised, not reproduced.