| Nurse practitioner | 431 |
| Physical therapist (private practice) | 384 |
| Internal medicine | 358 |
| Family practice | 292 |
| Physician assistant | 231 |
| Emergency medicine | 201 |
| Clinical psychologist | 163 |
| Anesthesiology | 144 |
| Optometrist | 122 |
| Obstetrics/gynecology | 115 |
| Hospitalist | 96 |
| Licensed clinical social worker | 83 |
| Diagnostic Radiology | 81 |
| Chiropractic | 71 |
| Psychiatry | 69 |
| Orthopedic surgery | 67 |
| Ophthalmology | 66 |
| Dermatology | 61 |
| Certified Registered Nurse Anesthetist (CRNA) | 60 |
| Mass Immunization Roster Billers | 57 |
| General surgery | 49 |
| Cardiology | 45 |
| Gastroenterology | 41 |
| Neurology | 36 |
| Critical care (intensivists) | 34 |
| Marriage and Family Therapist | 34 |
| Occupational therapist (private practice) | 30 |
| Urology | 30 |
| Mental Health Counselors | 29 |
| General practice | 28 |
| Physical medicine and rehabilitation | 28 |
| Podiatry | 27 |
| Otolaryngology | 26 |
| Hematology/oncology | 26 |
| Pathology | 26 |
| Nephrology | 24 |
| Pulmonary disease | 21 |
| Geriatric medicine | 21 |
| Vascular surgery | 20 |
| Audiologist (billing independently) | 19 |
| Radiation oncology | 19 |
| Registered Dietician/Nutrition Professional | 19 |
| Pediatric medicine | 16 |
| Endocrinology | 16 |
| Infectious disease | 16 |
| Pharmacy | 14 |
| Ambulatory Surgical Center | 14 |
| Centralized Flu | 14 |
| Neurosurgery | 13 |
| Speech / language pathology | 13 |
| Allergy/immunology | 12 |
| Interventional radiology | 12 |
| Clinical Laboratory (Billing Independently) | 11 |
| Interventional Cardiology | 11 |
| Rheumatology | 11 |
| Medical oncology | 11 |
| Pain Management | 10 |
| Plastic and reconstructive surgery | 10 |
| Certified nurse midwife | 9 |
| Thoracic surgery | 9 |
| Unknown physician specialty | 6 |
| Ambulance Service Supplier, e.g., private ambulance companies, funeral homes | 6 |
| Hospice and Palliative Care | 6 |
| Cardiac surgery | 5 |
| Certified clinical nurse specialist | 4 |
| Cardiac Electrophysiology | 4 |
| Sports Medicine | 4 |
| Interventional Pain Management (IPM) | 4 |
| Advanced Heart Failure and Transplant Cardiology | 3 |
| Gynecologist/oncologist | 3 |
| Epileptologists | 3 |
| Psychologist (billing independently) | 3 |
| Independent Diagnostic Testing Facility (IDTF) | 3 |
| Sleep Medicine | 3 |
| Addiction medicine | 3 |
| Osteopathic manipulative therapy | 2 |
| Surgical oncology | 2 |
| Neuropsychiatry | 2 |
| Nuclear medicine | 2 |
| Opioid Treatment Program | 2 |
| Medicare Diabetes Preventive Program | 2 |
| Maxillofacial surgery | 2 |
| General Psychiatry | 2 |
| Portable X-Ray Supplier (Billing Independently) | 1 |
| Home Infusion Therapy Services | 1 |
| Hand surgery | 1 |
| Oral surgery (dentists only) | 1 |
| Medical Genetics and Genomics | 1 |
| Unknown Provider | 1 |
| Peripheral vascular disease | 1 |
| Hematology | 1 |
| Public Health or Welfare Agencies (Federal, State, and local) | 1 |
| Colorectal surgery (formerly proctology) | 1 |