A client with bipolar disorder on lithium has an assessment; which finding supports the provider's request for laboratory evaluation?

• A. Sleeplessness and tremors that started yesterday
• B. Nausea for several days
• C. Weight gain over several weeks
• D. Dizziness after standing

Answer: (A)

Lithium has a very narrow therapeutic window, so new neurologic symptoms can signal rising levels and possible toxicity. Sleeplessness and tremors that started yesterday are red flags for lithium toxicity and justify immediate laboratory evaluation to check the serum lithium level and assess kidney and thyroid function. Tremor and CNS agitation reflect possible drug effect at higher levels, whereas the other findings—nausea over several days, weight gain, or dizziness on standing—are less specific and can occur for other reasons; they do not as clearly indicate the need for urgent labs. Ordering a serum lithium level along with renal function (BUN/creatinine), electrolytes, and thyroid studies helps guide safe dosing and identify if toxicity is developing.