It depends
If you are coding the primary E/M based on key elements, no, you don't need to document the time spent.
If you are coding the primary E/M based on counseling/coordination of care (i.e. time), then, YES, you have to have to entire time spent face-to-face with the patient, including the basic E/M code as well as the prolonged service (if applicable).
Hope that helps.
F Tessa Bartels, CPC, CEMC