A nurse is preparing to administer digoxin to a client who has heart failure. For which of the following findings should the nurse withhold the medication and report to the provider?

A. Serum potassium 4.8 mEq/L: Potassium is within/near normal-high range; digoxin toxicity risk increases with low K⁺, so this value alone is not a reason to withhold. B. Urine output 35 mL/hr: This is borderline but generally acceptable (oliguria is usually <30 mL/hr); not an absolute reason to withhold digoxin. C. Heart rate 66/min: Digoxin is typically withheld for significantly low heart rates (commonly <60/min); 66/min is usually acceptable to give with caution. D. Report of blurred vision: Blurred or yellow-green vision is a sign of digoxin toxicity - the nurse should withhold the medication and report to the provider.