In diabetes insipidus, which electrolyte abnormality is most associated with seizures?

• A. Hyponatremia
• B. Hypernatremia
• C. Hypokalemia
• D. Hyperkalemia

Answer: (B)

In diabetes insipidus, the lack of antidiuretic hormone causes kidney tubules to excrete a large amount of dilute urine. If water intake can’t keep up, you lose free water faster than you replace it, which raises serum osmolality and sodium—hypernatremia. This high sodium outside the cells pulls water out of brain cells, leading to cellular dehydration and brain shrinkage, which increases neuronal excitability and lowers the seizure threshold. So the electrolyte abnormality most linked to seizures in this context is hypernatremia. Hyponatremia would cause seizures through a different mechanism (brain swelling), but it’s not the pattern seen with DI.