What is lithium and what must be monitored during treatment?

Lithium is a mood stabilizer and first-line treatment for bipolar disorder, effective for acute mania and long-term prevention of manic and depressive episodes. It has a very narrow therapeutic index with a therapeutic range of 0.6 to 1.2 milliequivalents per liter. Lithium levels, kidney function, and thyroid function must be monitored regularly because lithium is excreted by the kidneys and can cause hypothyroidism and nephrogenic diabetes insipidus. Signs of lithium toxicity include tremor, nausea, diarrhea, confusion, and seizures.