“I’ve had a sickness bug and now I’m shaky and muddled — I’m on lithium”

An unwell patient on long-term lithium with new neurological symptoms — coarse tremor, unsteadiness/ataxia and confusion — after vomiting and diarrhoea must be assumed to have LITHIUM TOXICITY until proven otherwise, because lithium has a narrow therapeutic index and dehydration from intercurrent illness reduces its clearance and raises the level; "is that relevant?" must be answered emphatically yes, and the picture must not be dismissed as "just the bug". Recognise the toxicity features — coarse tremor (versus the fine tremor of therapeutic use), ataxia, slurred speech, myoclonus, drowsiness/confusion, GI upset, and in severe cases seizures, renal failure, arrhythmia and coma — and distinguish them from the precipitating viral illness. Act urgently: STOP lithium and, because confusion, ataxia and a coarse tremor are already present, arrange same-day hospital assessment for an urgent lithium level, renal function/U&E and rehydration (999 if drowsy, fitting or deteriorating) — lithium toxicity can be life-threatening, can occur even with a level in range in an unwell patient, and severe cases may need haemodialysis — rather than continuing lithium, waiting for a routine test or sending her home; thyroid function and calcium belong to the later monitoring review (NICE CG185, 2014). Identify and address the precipitants: dehydration from the D&V is the obvious one, but review interacting drugs that raise lithium (NSAIDs, ACE inhibitors/ARBs, and thiazide diuretics) and low salt, stopping offenders and correcting fluid/salt balance. Reinforce lithium sick-day rules and safety (maintain fluids and seek advice early in dehydrating illness, avoid NSAIDs, check interactions with new medicines, know toxicity symptoms, attend regular monitoring, carry the lithium alert card and record book — NPSA/2009/PSA005). The hidden agenda is the patient rationalising it as "just the bug" and underplaying the confusion — the daughter’s concern is the key signal; take the physical emergency seriously and act, while remaining mindful of her bipolar disorder so that lithium is re-established safely with psychiatric input once recovered, given relapse risk.