Katherine Streeter for NPR
Vidhya Nagarajan for NPR

Nurse Practioner Tina Clark examines Anastacia Casperson at the Glide Health Clinic in San Francisco. Andrew Nixon / Capital Public Radio/Flickr hide caption

itoggle caption Andrew Nixon / Capital Public Radio/Flickr

Shanda Johnson, right, a nurse practitioner, interviews patient Bill Gilligan at a MinuteClinic at the CVS drug store in North Brunswick, N.J. Mike Derer/AP hide caption

itoggle caption Mike Derer/AP