Which electrolyte abnormality is most likely with loop diuretic use?

Which electrolyte abnormality is most likely with loop diuretic use?

• A. Hyperkalemia
• B. Hypokalemia
• C. Hypercalcemia
• D. Hypermagnesemia

Answer: (B)

Loop diuretics block the Na-K-2Cl transporter in the thick ascending limb, so more sodium reaches the distal nephron. That increased Na+ delivery to the collecting duct drives more Na+ reabsorption in exchange for K+ and H+ secretion, leading to potassium wasting in the urine. The result is hypokalemia, the most common electrolyte disturbance with loop diuretic use. These drugs can also cause loss of magnesium and calcium in the urine (hypomagnesemia and increased calcium excretion), but the standout electrolyte change you’d expect clinically is low potassium. Hyperkalemia would be unlikely with loop diuretics (more typical of potassium-sparing scenarios), and hypercalcemia is not expected because calcium loss in urine is increased rather than retained.

Loop diuretics block the Na-K-2Cl transporter in the thick ascending limb, so more sodium reaches the distal nephron. That increased Na+ delivery to the collecting duct drives more Na+ reabsorption in exchange for K+ and H+ secretion, leading to potassium wasting in the urine. The result is hypokalemia, the most common electrolyte disturbance with loop diuretic use. These drugs can also cause loss of magnesium and calcium in the urine (hypomagnesemia and increased calcium excretion), but the standout electrolyte change you’d expect clinically is low potassium. Hyperkalemia would be unlikely with loop diuretics (more typical of potassium-sparing scenarios), and hypercalcemia is not expected because calcium loss in urine is increased rather than retained.