Internal Medicine: Medicare enrollment by state

Taxonomy codes for internal medicine

CMS's crosswalk maps 26 NUCC taxonomy codes to Medicare specialty 11. A provider enrolling as internal medicine should hold one of them as the primary taxonomy on their NPI.

Where it is concentrated

Raw counts follow population, so the more telling figure is each state's share: what fraction of the state's Medicare-enrolled NPIs are internal medicine. Nationally the specialty is 5% of enrolled NPIs. The highest shares are in California (6.8%), District of Columbia (6.5%), Rhode Island (6.5%); the lowest in North Dakota (1.8%), Alaska (1.9%), Nebraska (2.3%). 51 of the 51 (50 states and DC) have at least one enrolled.

Billing versus order-and-refer enrollment

Medicare enrolls practitioners in two ways. A full enrollment lets the provider bill Medicare for their own services; it is what the 128,064 above count. An order-and-refer-only enrollment lets a provider who never bills Medicare — a resident, a VA or military physician, a dentist ordering imaging — still order tests, equipment and referrals that Medicare pays for. 31,734 internal medicine NPIs hold that limited enrollment.

Every state

Counts are unique NPIs enrolled in each state; a provider enrolled in two states counts in both. The share is of all Medicare-enrolled NPIs in that state.

Sources: CMS Medicare Fee-For-Service Public Provider Enrollment, extract of 2026-09-29; CMS Medicare Provider and Supplier Taxonomy Crosswalk, August 2026. Checked 2026-10-24. Methodology.