Which statement correctly describes lithium's therapeutic serum range and early signs of toxicity?

• A. 0.8–2.0 mEq/L; early signs include weight gain and dry mouth.
• B. 0.6–1.2 mEq/L; early signs include GI upset, coarse tremor, confusion, and ataxia.
• C. 1.5–2.5 mEq/L; early signs include fever and tachycardia.
• D. 0.2–0.6 mEq/L; early signs include dizziness.

Answer: (B)

Lithium has a narrow therapeutic window, so keeping serum levels within a careful range is essential for effectiveness and safety. The maintenance range is about 0.6–1.2 mEq/L. Early signs of toxicity reflect CNS and GI irritation and typically include gastrointestinal upset, a coarse tremor, confusion, and ataxia. These symptoms appear before more severe toxicity and help clinicians recognize when to adjust the dose or check levels. Higher ranges are associated with more serious effects, whereas fever and tachycardia are not classic early signs, and dizziness alone isn’t a reliable early indicator. So the statement that describes a maintenance range around 0.6–1.2 mEq/L with early signs of GI upset, coarse tremor, confusion, and ataxia best fits clinical practice.