Lithium toxicity is rarely a dosing error. It is usually an ordinary event happening to a patient on a stable dose: a gastroenteritis, a heatwave, a fast, a new antihypertensive, a course of a non-steroidal for back pain. Each reduces renal clearance, and the therapeutic window is narrow enough that none of them needs to be dramatic.
The counselling that prevents this is given at initiation, when the patient is unwell and absorbing little, and then almost never repeated. Make it a recurring item at review rather than a one-off at the start. The content is short: hold the dose and seek advice during vomiting, diarrhoea or a fever with poor intake; keep salt and fluid intake steady rather than suddenly increasing or cutting either; check before starting an NSAID, an ACE inhibitor, an angiotensin receptor blocker or a diuretic; and treat coarse tremor, unsteadiness, confusion or slurred speech as toxicity until a level says otherwise.
In Indian practice, add the two that matter locally — summer heat with heavy sweating, and religious fasting. Neither is a reason to stop lithium. Both are reasons to plan for it in advance rather than to discover it in the emergency department.
- Repeat sick-day rules at every review, not only at initiation.
- Ask specifically about over-the-counter NSAIDs; patients do not report them as medicines.
- Plan fasting and hot-weather periods in advance, including when to check a level.
- Give the patient a written card with the hold rules and the toxicity symptoms.
- Take a level any time a patient on lithium presents acutely unwell, whatever the presenting complaint.
Why it matters
Most lithium toxicity arrives through an ordinary illness or an ordinary new prescription, not through a dosing mistake.
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