Quick reference: U.S. credentialing authorities

How federal and state authorities interact

The CMS National Plan and Provider Enumeration System assigns a single 10-digit National Provider Identifier that follows a clinician across state moves and employer changes. The NPI is necessary for every Medicare and Medicaid claim, but it does not, by itself, confirm that the provider currently holds an active state license, that authorization is delegated to each state medical board under the Tenth Amendment. Browse PlainDoctor by state to see how providers register practice locations.

Why specialty board certification matters

Board certification by an American Board of Medical Specialties member board signals voluntary post-licensure examination and ongoing Maintenance of Certification cycles. It is not legally required to practice medicine, but health plans, hospital credentialing committees, and patients increasingly use it as a quality signal. View specialty-level data through PlainDoctor specialty pages showing certification rates by jurisdiction.

Reading disciplinary records responsibly

State medical board orders are public legal documents that describe the factual findings, conclusions of law, and disciplinary action taken. A single malpractice payment does not necessarily indicate poor practice, high-risk specialties (neurosurgery, obstetrics) have higher baseline payment rates than primary care. Patterns of multiple actions, license restrictions, or revocations are the meaningful signals to weigh. Read the PlainDoctor methodology for how disciplinary data integrates into provider profiles.

Primary Care: Your Starting Point

Primary care physicians (PCPs) are generalists who manage a broad range of health conditions, provide preventive care, coordinate referrals, and serve as the entry point to the healthcare system. There are three main primary care specialties:

Family Medicine physicians care for patients across all ages and both sexes. Their training covers pediatrics, adult medicine, obstetrics, geriatrics, and mental health in a single residency. Family physicians are particularly common in rural and underserved areas where subspecialists may not be available.

Internal Medicine physicians (internists) specialize in adult medicine. They manage complex, chronic, and multi-system disease in adult patients. Internal medicine residency is three years, and many internists go on to subspecialty fellowship training (see below).

Pediatrics physicians care for patients from birth through young adulthood. Pediatric residency is three years, and like internal medicine, many pediatricians pursue fellowship subspecialties such as pediatric cardiology, pediatric neurology, or neonatology.

Other providers who often function as PCPs include geriatricians (specialists in older adult care), obstetrician-gynecologists (OB/GYNs) for women's health, and nurse practitioners or physician assistants practicing in primary care settings. Use PlainDoctor's search to find providers by name, or browse by state to see what's available near you.

When You Need a Specialist

Specialists complete additional residency training beyond medical school, and many complete further fellowship training, to focus on a specific organ system, patient population, or set of procedures. Seeing the right specialist can make a significant difference for complex or chronic conditions.

Generally, a referral to a specialist is appropriate when: your primary care physician identifies a condition outside their scope; you need a diagnostic procedure only specialists perform; a chronic condition requires subspecialty management; or you are seeking a second opinion on a diagnosis or treatment plan.

Many insurance plans require a referral from your PCP before covering a specialist visit (this is called a "gatekeeper" model). PPO plans and some HMOs allow self-referral to specialists, but out-of-pocket costs may be higher. Always check your plan's requirements before booking a specialist appointment.

Major Specialty Categories

Medical specialties broadly fall into several categories based on approach and training:

Medical specialties (non-surgical) use medications, procedures, and monitoring to manage disease. Examples include cardiology (heart), gastroenterology (digestive system), pulmonology (lungs), nephrology (kidneys), endocrinology (hormones and metabolism), rheumatology (joints and autoimmune disease), and hematology/oncology (blood disorders and cancer).

Surgical specialties treat conditions primarily through operative intervention. General surgery covers abdominal and soft tissue procedures. Other surgical specialties include orthopedic surgery (bones, joints, spine), neurosurgery (brain and nervous system), cardiothoracic surgery (heart and chest), vascular surgery, urology (urinary tract and male reproductive system), and plastic/reconstructive surgery.

Hospital-based specialties provide services primarily to inpatients. Radiology reads and interprets imaging studies. Anesthesiology manages sedation and pain control during procedures. Pathology diagnoses disease by analyzing tissue samples, biopsies, and lab tests. Emergency medicine manages acute illness and injury.

Behavioral and mental health specialties include psychiatry (MD/DO prescribers), psychology (PhD/PsyD, non-prescribers), and neuropsychology.

Allied health and non-physician specialties in the NPPES registry include dentistry, optometry, physical therapy, occupational therapy, speech-language pathology, chiropractic, podiatry, and pharmacy.

Sub-Specialties and Fellowship Training

Many medical and surgical specialties have recognized sub-specialties that require fellowship training, an additional 1–3 years of supervised training after completing a primary specialty residency. Fellowship-trained subspecialists have the deepest expertise in their narrow area.

Some common examples of internal medicine subspecialties (reached through internal medicine residency + fellowship):

• Cardiology - Heart disease; sub-subspecialties include interventional cardiology (angioplasty, stents) and electrophysiology (heart rhythm disorders)
• Gastroenterology - Digestive system; includes hepatology (liver disease) and advanced endoscopy
• Pulmonology / Critical Care Medicine - Lung disease and ICU care
• Infectious Disease - Complex infections, HIV, tropical medicine
• Geriatric Medicine - Care of older adults with multiple comorbidities
• Palliative Care - Symptom management and end-of-life care

Surgical subspecialties (reached through general surgery residency + fellowship) include colorectal surgery, surgical oncology, minimally invasive/bariatric surgery, and trauma/acute care surgery.

Orthopedic subspecialties include sports medicine, spine surgery, joint replacement, hand surgery, and pediatric orthopedics. Neurosurgery subspecialties include spine, cerebrovascular (aneurysm/stroke), neuro-oncology, and functional neurosurgery (deep brain stimulation).

Understanding Taxonomy Codes in NPI Data

Every provider's NPI record includes one or more NUCC Health Care Provider Taxonomy Codes, a standardized classification system maintained by the National Uniform Claim Committee. These 10-character alphanumeric codes identify a provider's type and specialty in a machine-readable format used across the healthcare system for billing, credentialing, and data analysis.

The taxonomy code structure has three levels: provider type (individuals vs. organizations), classification (the broad specialty), and specialization (the sub-specialty). For example:

• 207Q00000X - Allopathic & Osteopathic Physicians / Family Medicine
• 207RC0000X - Allopathic & Osteopathic Physicians / Internal Medicine / Cardiovascular Disease
• 207RI0011X - Allopathic & Osteopathic Physicians / Internal Medicine / Interventional Cardiology
• 363L00000X - Nurse Practitioner
• 363A00000X - Physician Assistant

PlainDoctor maps these taxonomy codes to readable specialty names displayed on provider profiles and in the specialty directory. The full NUCC taxonomy code set includes over 900 distinct codes covering every recognized provider type in U.S. healthcare.

Providers can list up to 15 taxonomy codes in their NPI record, with one designated as the primary taxonomy. When a provider's primary taxonomy shows a broad specialty (like "Internal Medicine"), they may practice general internal medicine or be a subspecialist whose secondary taxonomy code reflects their fellowship training.

Frequently Asked Questions