Which condition increases the risk of lithium toxicity?

Which condition increases the risk of lithium toxicity?

• A. Dehydration
• B. Overhydration
• C. High sodium intake
• D. Regular exercise

Answer: (A)

Lithium is handled by the kidneys in a way that ties closely to hydration and sodium balance. When you’re dehydrated, the kidneys conserve water and sodium, and lithium follows that same reabsorption pathway. The result is more lithium reabsorbed into the bloodstream, raising serum levels and the risk of toxicity. That’s why dehydration increases the risk. If you overhydrate, the opposite tends to happen—more lithium is excreted and serum levels can drop, reducing toxicity risk. A high sodium intake also promotes excretion of sodium and water, which tends to decrease lithium reabsorption. Regular exercise by itself isn’t a direct risk factor for lithium toxicity unless it leads to dehydration.

Lithium is handled by the kidneys in a way that ties closely to hydration and sodium balance. When you’re dehydrated, the kidneys conserve water and sodium, and lithium follows that same reabsorption pathway. The result is more lithium reabsorbed into the bloodstream, raising serum levels and the risk of toxicity. That’s why dehydration increases the risk.

If you overhydrate, the opposite tends to happen—more lithium is excreted and serum levels can drop, reducing toxicity risk. A high sodium intake also promotes excretion of sodium and water, which tends to decrease lithium reabsorption. Regular exercise by itself isn’t a direct risk factor for lithium toxicity unless it leads to dehydration.