A nurse is planning to administer digoxin to a client who has heart failure. Which of the following laboratory results is the priority for the nurse review prior to administering the medication?

A. Blood urea nitrogen assesses kidney function but is less directly related to digoxin toxicity risk. B. Creatinine also reflects kidney function but is not the highest priority in this context. C. Hemoglobin levels are not directly related to digoxin administration. D. Potassium levels are critical to review because hypokalemia increases the risk of digoxin toxicity, and hyperkalemia can also affect the drug's efficacy. Monitoring potassium is essential before giving digoxin.