Which laboratory test result is most important for a nurse to check before administering furosemide (Lasix) to a client with heart failure?

Before administering furosemide, also known as Lasix, it is crucial for a nurse to check the potassium level. This medication is a loop diuretic, which promotes the excretion of sodium and water but can also lead to the loss of potassium. Hypokalemia, or low potassium levels, can result in serious complications, including cardiac arrhythmias.

Monitoring the potassium level prior to administration allows the nurse to assess the risk of potential side effects and to determine if potassium supplementation or other interventions are necessary to maintain the client’s electrolyte balance. This proactive step helps ensure patient safety and effective management of heart failure.

While the other laboratory tests, such as creatinine, cholesterol, and blood urea nitrogen, are important in assessing renal function, lipid levels, and hydration status respectively, they do not present as immediate a risk for adverse effects from furosemide as abnormal potassium levels do.