Final answer:
In hyperparathyroidism, the nurse should not administer oral phosphate to the patient with an elevated serum calcium level.
Step-by-step explanation:
In hyperparathyroidism, the serum calcium level is elevated. In this case, the serum calcium level of the patient is 12.5 mg/dL, which is significantly above the normal range. Therefore, it would be inappropriate to administer oral phosphate to the patient, as this would further increase the serum calcium level. Instead, the nurse should consult with the healthcare team to determine the appropriate course of action for the patient.