A nurse is receiving a telephone prescription for a client and documents it as metformin 500 PO BID. Which of the following elements should the nurse identify is missing from the prescription?

A. Dosage: The prescription states "metformin 500" but does not specify milligrams (mg), making it incomplete. It should be "metformin 500 mg PO BID" to avoid errors. B. Time/frequency: BID (twice a day) is included, so the frequency is already specified. C. Route: PO (by mouth) is clearly stated. D. Medication: The drug name "metformin" is provided, so it is not missing.