An adult client who is admitted to the mental health unit for treatment of bipolar disorder has a slightly slurred speech pattern and an unsteady gait. Which assessment finding is most important for the nurse to report to the healthcare provider? Reference Range: Blood alcohol level (0 to 0.05% (0 to 10.9 mmol/L] Lithium [0.8 to 1.2 mEq/L (0.8 to 1.2 mmol/L)]

A. A blood alcohol level of 0.09% indicates intoxication but is less immediately critical than lithium toxicity. B. A serum lithium level of 1.6 mEq/L indicates lithium toxicity, which can be life- threatening and requires immediate medical intervention. C. Significant weight loss is concerning but not as acute an issue as potential lithium toxicity. D. Lack of sleep is serious but is a symptom that can be managed; it is not as urgent as addressing potential lithium toxicity.