Final answer:
The initial action when a patient is referred to a medical office should be to schedule the patient's appointment, followed by obtaining insurance information and coordinating with the referring physician.
Step-by-step explanation:
When a patient is referred to a medical office, the most appropriate initial action for the medical assistant is to schedule the patient's appointment. This is the first step in ensuring the patient receives the necessary care. Once the appointment is scheduled, obtaining the patient's insurance information is also important for administrative purposes. Coordination with the referring physician for more details about the patient's condition and required medical history can follow the scheduling of the appointment. Checking the patient's vital signs would typically occur during the patient's visit, not at the scheduling phase.