Lithium Toxicity
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Direct answer
Lithium toxicity is the clinical syndrome caused by serum lithium rising above the therapeutic range (commonly above 1.5 mEq/L, though chronic toxicity can occur at lower levels with dehydration and interacting drugs), because lithium has a narrow therapeutic index, is not metabolised, and is excreted entirely by the kidney. Early features are coarse tremor, nausea, vomiting and diarrhoea, progressing to cerebellar signs — ataxia, dysarthria, incoordination — then confusion, seizures, arrhythmia, coma and death. Management is immediate cessation of lithium, correction of fluid and electrolyte status, and haemodialysis for severe or symptomatic cases with high levels.
What you must remember
- Pharmacological root cause: lithium is entirely renally excreted and reabsorbed with sodium in the proximal tubule; anything reducing glomerular filtration or sodium delivery (dehydration, low-salt diet, diuretics, NSAIDs, ACE inhibitors) raises levels sharply.
- Level bands: therapeutic commonly 0.6-1.2 mEq/L; toxicity generally above 1.5, moderate-to-severe features above 2.0 and severe poisoning above 2.5-3.0 — in chronic toxicity the level correlates poorly with severity and symptoms trump numbers.
- Clinical ladder: GI upset and coarse tremor early, then ataxia and dysarthria, then confusion and neuromuscular irritability, progressing to seizures, arrhythmias, coma and renal failure; chronic toxicity may mimic dementia.
- Immediate management: stop lithium, hold interacting drugs, check the level, correct dehydration and electrolytes, and monitor cardiac rhythm, renal function and neurology.
- Haemodialysis: for severe symptomatic poisoning — commonly above about 4.0 mEq/L acutely or 2.5 mEq/L chronically, or with renal failure or deteriorating neurology; lithium redistributes after dialysis, so repeated sessions may be needed.
- Prevention protocol: counsel on fluids during gastroenteritis, sweating and heat; avoid NSAIDs and monitor levels, creatinine, electrolytes, calcium and TSH every three to six months when stable.
Common confusion
Chronic versus acute toxicity is the concept examiners probe: acute overdose produces predominantly GI then neurologic signs with very high measured levels but often milder symptoms (little body store yet), whereas chronic accumulation produces neurotoxicity at lower measured levels and carries a worse prognosis — severity, not the number alone, drives dialysis decisions. Lithium fine therapeutic tremor versus the coarse tremor of toxicity is a close second discriminator. Finally, do not attribute new ataxia or confusion in a lithium patient to "mental illness" — check the level first, always.
Exam-focused takeaway
NEET-PG presents a bipolar patient on lithium started on an NSAID or thiazide, or with vomiting and dehydration, who develops coarse tremor, ataxia and confusion — the answers are check serum lithium, stop the drug and interacting agents, hydrate, and haemodialyse severe cases. One-liners test the 1.5 mEq/L threshold, the four level-raising drug groups, cerebellar signs as the hallmark, and complete renal excretion as the reason levels climb in renal impairment. Prevention counselling — maintain salt and fluid intake during illness — is a standard communication-style stem.
Frequently asked questions
At what lithium level does toxicity usually begin?
Commonly above 1.5 mEq/L; in chronic poisoning and renal impairment it can appear at lower levels.
Which drugs precipitate lithium toxicity?
NSAIDs, thiazides, ACE inhibitors and ARBs, plus dehydration, salt restriction and renal impairment.
What are the early clinical features of lithium toxicity?
Coarse tremor, nausea, vomiting and diarrhoea, then cerebellar ataxia, dysarthria and confusion.
When is haemodialysis indicated in lithium poisoning?
In severe symptomatic poisoning — commonly above about 4.0 mEq/L acutely or 2.5 mEq/L chronically, and with renal failure or deteriorating neurology.
Why does chronic toxicity behave differently from acute overdose?
Tissue stores are loaded, so neurotoxicity occurs at lower levels with worse outcomes.
How is lithium toxicity prevented?
Fluid and salt counselling during illness, avoidance of level-raising drugs, and regular monitoring of levels and renal function.