A 28-year-old woman with bipolar disorder is taking lithium to control her symptoms. A test of her lithium level reveals a value of 2.3 mEq/L (normal range 0.6-1.25 mEq/L). Which of the following side effects is most likely to occur?

Lithium is used primarily for bipolar affective disorder, either to treat mania or prevent recurrences of the bipolar disorder. It has also been used in severe unipolar depression. Acute intoxication can result in vomiting, diarrhea, tremor, ataxia, coma, and convulsions. Leukocytosis is also a side effect of lithium therapy. Polyuria and polydipsia secondary to acquired nephrogenic diabetes insipidus is a common side effect and results in hypernatremia. Both acute and chronic intoxication can be lethal. The toxic and therapeutic levels of lithium are very close, and patients on lithium require close medical observation, including measurement of serum lithium levels.