Nursing care
Lithium: what to check before you give it
Written and reviewed by Dana Whitfield, RN, MSN · 4 min read · Updated September 2026
Short answer
Lithium has a narrow therapeutic range of 0.6–1.2 mEq/L, and levels can shift dangerously with anything that changes sodium or fluid balance — dehydration, a hot day, vomiting or a new diuretic can all push a patient into toxicity. Nurses must check recent levels, hydration and sodium intake before administering each dose.
Mechanism, simply
Lithium is a mood stabiliser whose exact mechanism is not fully understood, but it is thought to work by altering sodium transport across neuronal membranes and modulating neurotransmitter activity, including glutamate and GABA signalling. It dampens the neuronal excitability associated with mania without the sedating effect of an antipsychotic.
What makes lithium clinically distinctive is that it behaves like a salt, not a typical drug. It is handled by the kidneys in competition with sodium — reabsorbed via the same pathways in the proximal tubule. That single fact explains almost everything else you need to know about giving it safely, from why dehydration is dangerous to why a low-sodium diet raises the level.
Indications you will see on the ward
Lithium is used first-line for bipolar disorder, both to treat acute manic episodes and, more commonly on a long-term basis, to prevent relapse into mania or depression. It is also used as an augmentation agent for treatment-resistant depression in some patients already on an antidepressant.
On an acute psychiatric unit you will most often see it started or re-titrated after a manic episode, with levels drawn regularly until the patient is stable on a maintenance dose. On a medical-surgical floor, lithium is more often relevant because the patient is already established on it and is now unwell with something — a GI illness, a fever, a new prescription — that threatens to alter the level.
Assessment before administration
Check the most recent lithium level before every dose where levels are being drawn, and know that the therapeutic range is 0.6–1.2 mEq/L, drawn as a trough level roughly 12 hours after the last dose. Levels above this range risk toxicity; levels below it risk an inadequately treated mood episode.
Assess hydration status and recent sodium intake specifically, because anything that changes sodium or fluid balance changes the lithium level — a hot day with heavy sweating, vomiting, diarrhoea, reduced oral intake, or a new low-sodium diet can all concentrate lithium in the blood and precipitate toxicity even without a dose change. Ask about recent illness, new medications, and fluid intake, and hold the dose and notify the prescriber if the patient shows any early toxicity signs or a level is due and outstanding.
Toxicity and the antidote
Early toxicity presents as a coarse tremor (distinct from the fine tremor seen at therapeutic levels), nausea, vomiting, diarrhoea, and ataxia. As levels climb further, expect confusion, slurred speech, muscle fasciculations, and eventually seizures, arrhythmias and coma at severe levels. These signs should prompt an immediate level check and dose hold.
Lithium has no pharmacological antidote. Management is supportive: stop the drug, correct fluid and electrolyte imbalance, and in moderate-to-severe toxicity use haemodialysis to remove lithium directly, since it is not protein-bound and dialyses well. This is worth knowing precisely because students often expect every toxic drug to have a reversal agent — lithium is a clear counterexample.
Interactions that matter
Thiazide diuretics reduce sodium reabsorption and, through that same competitive pathway, increase lithium reabsorption and raise the level significantly — this combination requires close monitoring or avoidance. NSAIDs reduce renal lithium clearance and can raise levels even at short-term over-the-counter doses, which is a common source of accidental toxicity.
ACE inhibitors and ARBs also raise lithium levels by altering renal sodium handling. Caffeine and osmotic diuretics can lower the level by increasing lithium excretion. Any new prescription, including something as ordinary as an NSAID bought without a script, should prompt a check of whether it interacts with lithium.
What the patient must be told
Patients need to understand that lithium level is not set-and-forget: it moves with their fluid and salt intake, and a hot day, a stomach bug, or heavy sweating during exercise is a clinical event, not just discomfort. They should maintain a consistent fluid intake of around 2 to 3 litres a day unless told otherwise, and maintain a steady salt intake rather than starting a sudden low-sodium diet.
Teach the early signs of toxicity — coarse tremor, vomiting, diarrhoea, confusion, slurred speech — and tell the patient to seek care and get a level checked if these appear. They should not stop the drug abruptly without medical advice, given the relapse risk in bipolar disorder, and should tell every prescriber and pharmacist they are on lithium before starting any new medication, including over-the-counter NSAIDs.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our mental health practice questions are the closest set to what this page covers.
Common questions
What is the therapeutic range for lithium?
0.6 to 1.2 mEq/L, measured as a trough level roughly 12 hours after the last dose. Levels above this range carry a risk of toxicity, and the range is narrow enough that regular monitoring is standard practice throughout treatment.
Why does dehydration matter so much for a patient on lithium?
Lithium is reabsorbed by the kidneys through the same pathway as sodium. Dehydration from any cause — heat, illness, reduced intake — concentrates lithium in the blood and can push a stable patient into toxicity without any change in dose.
What is the antidote for lithium toxicity?
There is no pharmacological antidote. Treatment is supportive — stopping the drug, correcting fluid and electrolytes, and using haemodialysis in moderate-to-severe toxicity, since lithium is not protein-bound and clears well through dialysis.
Can a patient on lithium take ibuprofen for a headache?
Not without checking first. NSAIDs reduce renal clearance of lithium and can raise the blood level significantly, even at standard over-the-counter doses, so patients should be taught to check with a prescriber or pharmacist before taking one.
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