Which of the following is the therapeutic serum lithium level for maintenance treatment of bipolar disorder?

Explanation

## Therapeutic Lithium Levels **Key Point:** The therapeutic serum lithium concentration for maintenance treatment of bipolar disorder is **0.6–1.2 mEq/L** (or mmol/L). ### Lithium Level Classification | Serum Level (mEq/L) | Clinical Status | Management | | --- | --- | --- | | < 0.3 | Subtherapeutic | Increase dose | | 0.6–1.2 | Therapeutic (maintenance) | Continue; monitor | | 1.2–1.8 | Therapeutic (acute mania) | Higher end for acute episodes | | 1.8–2.5 | Mild toxicity | Reduce dose; monitor | | 2.5–3.5 | Moderate toxicity | Hold dose; supportive care | | > 3.5 | Severe toxicity | Emergency management; dialysis | **High-Yield:** Maintenance levels (0.6–1.2 mEq/L) are lower than acute treatment levels (1.2–1.8 mEq/L) to minimize toxicity risk while maintaining efficacy. ### Clinical Pearl **Timing of sampling:** Serum lithium levels should be drawn **5–7 days after initiation** or dose change, and **12 hours post-dose** (at trough) to ensure steady-state measurement and consistency. **Narrow therapeutic index:** Lithium has a narrow margin between therapeutic and toxic levels, requiring regular monitoring (baseline, then every 3–6 months during maintenance).