If Mr. Duncan reports feeling weak, what should the nurse's priority action be?

The priority action of assessing vital signs is crucial when a patient, like Mr. Duncan, reports feeling weak. Vital signs provide immediate and essential information about the patient’s current physiological status. This includes heart rate, blood pressure, respiratory rate, and temperature. Changes in these vital signs can indicate underlying issues such as potential dehydration, infection, or other critical medical conditions that could explain the patient's weakness.

By assessing vital signs first, the nurse can identify any abnormalities that may require urgent interventions. For example, if the blood pressure is low or the heart rate is elevated, the nurse can take appropriate measures to stabilize the patient. Understanding these vital indicators helps direct further actions, such as whether fluid replacement or other interventions are needed.

Other options, while important, do not address the immediate need for a comprehensive understanding of Mr. Duncan’s condition. Documenting findings is essential but typically follows the assessment. Administering fluid replacement is a potential intervention, but it should be grounded in the findings from the initial assessment. Providing nutritional education is also beneficial but is not an immediate response to a report of weakness. Thus, assessing vital signs is the most appropriate first step to ensure the patient's safety and guide further care.