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Lithium Monitoring — MRCPsych Paper B MCQ

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ModerateMood DisordersLithium MonitoringMRCPsych Paper B

A 40-year-old man with bipolar disorder has taken a stable dose of lithium 1000 mg daily for 18 months. He is clinically stable and adherent, takes no medicines that interact with lithium, and has no renal, thyroid or calcium abnormalities. His last plasma lithium concentration was 0.7 mmol/L. He attends his scheduled 6-monthly lithium review. According to NICE CG185, which monitoring package should be performed?

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Correct answer: A — Plasma lithium concentration, weight or BMI, urea and electrolytes including calcium, eGFR, and thyroid function

The correct answer is A. NICE recommends measuring plasma lithium every 6 months after the first year in low-risk patients. Monitoring should remain every 3 months in specified higher-risk groups, including older people, those taking interacting medicines, those with poor adherence or symptom control, and those whose last lithium concentration was at least 0.8 mmol/L. Weight or BMI, urea and electrolytes including calcium, eGFR and thyroid function are required every 6 months for everyone established on lithium. Option D omits essential toxicity monitoring. Option C resembles the broader annual physical health assessment for bipolar disorder but does not replace lithium-specific monitoring. Prolactin testing is principally relevant to prolactin-raising antipsychotics and is not routine lithium monitoring. An ECG is indicated when initiating lithium in someone with cardiovascular disease or risk factors, not routinely at each review.

Reference: National Institute for Health and Care Excellence. Bipolar disorder: assessment and management (CG185), sections 1.10.19–1.10.21. Published 2014; updated 2 September 2025. https://www.nice.org.uk/guidance/cg185/chapter/recommendations