Final answer:
The nurse should immediately clarify the prescription with the primary healthcare provider (PHCP) to ensure medication safety and to confirm whether the higher dose is intentional or a mistake.
Step-by-step explanation:
When a nurse notes that a client's prescribed dose is twice the amount the client reported taking before admission, the most appropriate nursing action is to clarify the prescription with the primary healthcare provider (PHCP). The nurse should ensure medication safety by verifying the accuracy of the prescription dosage before administration. The nurse should cross-reference the client's medical records, the medication prescription sheet, and communicate any discrepancies with the PHCP to determine whether the prescribed dose is intended or an error. It is crucial to advocate for the patient's safety and provide the correct dosage according to the PHCP's instructions.