This page compares two distinct NUCC-taxonomy specialties tracked by the CMS National Plan and Provider Enumeration System: Internal Medicine Physician, which currently counts 172,737 enrolled providers across 56 U.S. states and territories, and Registered Nurse, with 177,204 providers across 56 states. Each clinician on these rosters selected a primary NUCC code at NPI enrollment, so the totals measure how many providers self-identify their primary practice as Internal Medicine Physician or Registered Nurse rather than the total population ever trained or credentialed in either field, dual-certified clinicians show up under whichever code they registered first. Every figure is drawn from the federal National Provider Identifier Registry (CMS NPPES) - more than 7 million providers, maintained since May 2007, with 2023 Medicare Part D data, and, according to CMS, can be searched, compared, and traced in our methodology.

On national volume, Registered Nurse carries the larger provider roster (177,204 vs 172,737), with both specialties present in the same 56 states. The top Internal Medicine Physician concentration sits in California (20,046 providers), while Registered Nurse peaks in New York (27,515). The per-capita columns in the table below normalize each state's raw count against 2023 Census population estimates, which matters because absolute provider counts track population scale first and specialty density second, a small state with a strong training pipeline can out-rank a larger state on per-100K availability.

Use this comparison to understand relative availability, not to judge clinical substitutability - Internal Medicine Physician and Registered Nurse are distinct specialties with different scopes of practice, training requirements, and conditions they treat, even when their NUCC categories overlap. Important: PlainDoctor is a directory of publicly available CMS government data, not medical advice, a provider rating, or a recommendation about which specialty a patient should consult. Always work with a licensed clinician to determine which specialty is appropriate for your condition, verify any specific provider through the NPPES NPI Registry and the relevant state medical board, and consult the NUCC taxonomy documentation for the formal scope-of-practice definitions behind each specialty code.