Final answer:
The nurse should withhold gentamicin and notify the provider if the serum creatinine level is elevated. Elevated serum creatinine can indicate renal impairment, and gentamicin can potentially be toxic to the body if renal function is compromised.
Step-by-step explanation:
The nurse should withhold the medication and notify the provider if the serum creatinine level from the client's medical record is elevated. Serum creatinine level is an important indicator of kidney function and an elevation in this level may suggest renal impairment. Gentamicin is primarily excreted by the kidneys, so if the client's renal function is compromised, the medication can accumulate in the body, leading to potential toxicity.