A nurse is caring for a female client who is receiving intravenous gentamicin. Which of the following laboratory values is the priority to report to the provider?

A. A sodium level of 146 mEq/L is only slightly above normal and is not a priority concern. B. A WBC count of 12,668/mm³ is mildly elevated, possibly indicating infection or inflammation, but this is not uncommon and not the most urgent issue in a client receiving gentamicin. C. A creatinine level of 2 mg/dL is elevated and is the priority finding because gentamicin is nephrotoxic. Elevated creatinine indicates impaired kidney function, which can worsen with continued use of gentamicin. This must be reported to the provider immediately. D. A hemoglobin level of 11.5 g/dL is slightly below normal for a female but is not urgent and does not indicate a critical condition in this context.