As of 2016, there were more than 222,000 nurse practitioners licensed in the United States, according to the American Association of Nurse Practitioners' National Nurse Practitioner Database.
Here are scope of practice laws for NPs in the country, as of July 24, 2015, from Kaiser State Health Facts. Thirty-two states and the District of Columbia allow NPs to provide care without physician involvement and 18 states do not.
NPs may diagnose/treat patients without physician involvement
1. Alaska
2. Arizona
3. Arkansas
4. Colorado
5. Connecticut
6. District of Columbia
7. Hawaii
8. Idaho
9. Iowa
10. Kentucky
11. Maine
12. Maryland
13. Massachusetts
14. Michigan
15. Minnesota
16. Montana
17. Nebraska
18. Nevada
19. New Hampshire
20. New Jersey
21. New Mexico
22. New York
23. North Dakota
24. Oklahoma
25. Oregon
26. Rhode Island
27. Tennessee
28. Utah
29. Vermont
30. Washington
31. West Virginia
32. Wisconsin
33. Wyoming
NPs may not diagnose/treat patients without the following types of physician involvement
Collaborative agreement — requires NPs and physicians establish a collaborative agreement before NPs can diagnose and treat patients
34. Alabama
35. Illinois
36. Indiana
37. Louisiana
38. Mississippi
39. Missouri
40. Ohio
41. Pennsylvania
42. South Dakota
43. Virginia
Physician supervision — requires physicians supervise NPs during diagnosis and treatment
44. California
45. Delaware
46. Florida
47. Georgia
48. Kansas
49. North Carolina
50. South Carolina
51. Texas