A nurse is caring for a client who is taking triamterene. For which of the following laboratory values should the nurse withhold the medication?

The correct answer is B: Potassium 5.3 mEq/L. Triamterene is a potassium-sparing diuretic, which helps retain potassium in the body. A potassium level of 5.3 mEq/L is within the normal range, but since triamterene can cause hyperkalemia (elevated potassium levels), the nurse should monitor potassium closely. With a potassium level of 5.3 mEq/L, there is a risk of further potassium accumulation with triamterene, so the medication should be withheld to prevent hyperkalemia. The other laboratory values (A, C, D) are within normal ranges and do not directly impact the use of triamterene.