Lithium therapy requires monitoring, and dialysis may be needed if lithium levels reach a certain concentration. At what concentration might dialysis be considered?

• A. 1.5 mmol/L
• B. 2.0 mmol/L
• C. 3.0 mmol/L
• D. 4.0 mmol/L

Answer: (C)

When a patient on lithium is toxic, the key decision is whether the amount in the blood is high enough and the situation severe enough to justify rapid removal of the drug. Dialysis is used in severe lithium toxicity or when there are signs of neurotoxicity or renal failure, because lithium is effectively cleared by dialysis. A serum concentration around 3.0 mmol/L is a common point at which clinicians start to consider dialysis, especially if the patient has symptoms such as confusion, tremor, seizures, or cardiac abnormalities, or if kidney function is impaired. Levels around 1.5–2.0 mmol/L are usually managed with stopping lithium and supportive care unless there are additional risk factors, while much higher levels (around 4.0 mmol/L or more) more clearly mandate dialysis. The choice of 3.0 mmol/L reflects the point at which dialysis becomes a reasonable consideration in the right clinical context.