Two numbers that don't fit together: 166,593 nurse practitioners are enrolled in Medicare under the Nurse Practitioner specialty designation, while just 39 NP or PA credentialed clinicians list Internal Medicine as their primary specialty. The workforce transformation everyone is debating in statehouses has already happened, just not where most people think.

The Workforce Has Already Reorganized Around Its Own Taxonomy

The Clinician Directory data makes one thing clear: non-physician clinicians have not infiltrated physician specialty categories. They've built parallel ones. Nurse Practitioners, at 253,746 total clinicians, are now the single largest specialty group in the dataset, ahead of Internal Medicine's 85,186 MDs. Physician Assistants, at 124,919, rank second among all specialty groups.

These aren't clinicians scattered across cardiology offices and surgical suites under physician specialty codes. The overwhelming majority list their credential type as their primary specialty. Of the 253,746 clinicians under the Nurse Practitioner specialty, 166,593 hold NP credentials. Of the 124,919 under Physician Assistant, 93,057 hold PA credentials. The workforce has effectively self-sorted into its own taxonomy, separate from the physician specialty hierarchy.

That separation matters for how we count and compare. When analysts cite NP and PA workforce growth as evidence of specialty care expansion, they're largely describing a workforce that identifies by credential, not by clinical domain. The scope-of-practice debate assumes these clinicians are substituting for physicians in specific specialties. The directory data suggests most are enrolled under their own category entirely.

Specialty Penetration Is Minimal Where It's Assumed to Be High

Where NPs and PAs do list a physician-defined specialty as their primary designation, the numbers are small. Family Practice ranks third among NP/PA specialties with just 126 clinicians, compared to 68,828 MDs in the same specialty. Emergency Medicine has 42 NP or PA credentialed clinicians listed under that specialty, against 31,400 MDs. Internal Medicine has 39.

Cardiology shows the same pattern at the state level. The highest NP or PA penetration in Cardiovascular Disease (Cardiology) in any single state is 0.2%, reached in both Wisconsin (1 NP out of 409 total) and Virginia (1 NP out of 537 total). California, with 2,014 cardiologists, has 2 NP-credentialed clinicians in that specialty, a 0.1% share. Most states have zero.

For patients and health systems expecting NPs and PAs to fill specialist gaps in cardiology or internal medicine, these numbers describe a very different reality than the policy conversation implies. The credential expansion is real. The specialist substitution, at least as captured in primary specialty designations, is not.

Where Non-Physician Credentials Already Dominate Completely

Several specialties have already completed a transition that cardiology hasn't started. Clinical Social Worker has 58,710 total clinicians with a 100% non-MD/DO rate. Physical Therapist in Private Practice has 87,157 clinicians, also at 100% non-MD/DO, including 58,035 with other credentials and 29,070 with no credential listed. Certified Registered Nurse Anesthetists number 55,202, with 50,910 holding CRNA credentials and a 99.9% non-MD/DO rate.

These specialties aren't contested. The workforce composition is settled, and the clinical roles are well-defined. The contrast with cardiology or internal medicine isn't just a matter of degree. It reflects two entirely different workforce structures operating under the same enrollment system.

The open question the data raises is structural: given that NP and PA credentialed clinicians number only 39 in Internal Medicine and 42 in Emergency Medicine as a primary specialty, do the 166,593 NPs and 93,057 PAs enrolled under their own specialty designations actually practice in physician-led specialty settings, and if so, how are those clinical roles captured in claims data? The directory tells us where clinicians are enrolled. It doesn't tell us where they work.