Lithium and other mood stabilisers: blood levels, toxicity signs, fluids and laboratory checks

Safe practice

Lithium works only in a narrow blood range: the nurse checks levels, fluids and salt, spots early toxicity and watches kidney and thyroid tests.

Updated Nov 13, 2026

Key points

Lithium level: drawn as ordered, usually 10–12 hours after the last dose. WHO's mhGAP gives a target of 0.6–1.0 mEq/L; the laboratory's range and the prescriber's target apply.
Early toxicity: diarrhoea, vomiting, drowsiness, muscle weakness, lack of coordination; then coarse tremor and confusion. Hold the dose and notify at once.
Later signs: unsteady gait, blurred vision, tinnitus, large volumes of dilute urine, confusion; very high levels are an emergency even without symptoms.
Steady fluid and salt intake; report vomiting, diarrhoea, heavy sweating or fever, which raise the level.
Lithium tests: kidney function, thyroid, calcium, ECG. Valproate: liver tests and platelets. Carbamazepine: blood count, liver, sodium. Lamotrigine: any rash.
Valproate, lithium and carbamazepine are avoided in pregnancy where possible: report pregnancy or plans at once.

What it is

Mood stabilisers treat and prevent mania. Lithium has a narrow margin: toxicity can occur at levels close to the useful ones, so it is given only where blood levels can be measured promptly. Dehydration, sweating, vomiting, diarrhoea, fever, low salt intake and some medicines (anti-inflammatories, thiazide diuretics, ACE inhibitors) raise the level. Anticonvulsants used as mood stabilisers (valproate, carbamazepine, lamotrigine) need their own laboratory and skin checks. The nurse monitors, teaches and reports; the prescriber sets and adjusts the dose.

What it requires

Baseline before lithium if possible: kidney and thyroid function, blood count, ECG and a pregnancy test (mhGAP).
A reliable laboratory for prompt drug levels, and a schedule of levels as ordered.
A fluid-balance chart when intake is poor, in hot weather, or with vomiting or diarrhoea.
A list of the medicines that raise lithium levels, shared with the person and the pharmacy.

Components

Drug-level monitoring and recognition of toxicity.
Fluid, salt and illness management (sick days).
Laboratory monitoring of kidney, thyroid, liver and blood, by medicine.
Teaching: adherence, warning signs, interactions, driving, pregnancy.

How it is applied (and why)

Arrange the lithium level at the ordered time after the last dose and record the time of that dose — a level drawn at the wrong time misleads.
Before each dose, ask about diarrhoea, vomiting, drowsiness, weakness or unsteadiness and look for coarse tremor — these are signs of toxicity.
If toxicity is suspected, hold the dose and notify the prescriber at once; call for help if confused or unsteady — lithium toxicity can kill.
Encourage regular fluids and usual salt, and record intake and output when ill — dehydration and low salt raise the lithium level.
Check the medicine list for anti-inflammatories, thiazide diuretics or ACE inhibitors and tell the prescriber — they raise lithium levels.
Follow up kidney, thyroid and calcium results and report thirst with heavy urination — lithium can harm the kidney, thyroid and parathyroids.
With valproate or carbamazepine, check ordered liver tests, blood counts and sodium and report jaundice, bleeding, fever or abdominal pain.
With lamotrigine, teach to report any rash or flu-like illness at once — it can start a rare, severe skin reaction (Stevens–Johnson).

In nursing practice

Fine hand tremor, mild thirst and passing more urine can persist on lithium; a coarse tremor or new confusion is not normal.
Lithium can change the ECG: teach to seek urgent help for fainting, palpitations or shortness of breath.
Stopping lithium suddenly or taking it erratically raises the risk of relapse; mhGAP advises against lithium where supply or level testing is unreliable.
Lithium can cause drowsiness at first: no driving or machinery until the person knows how it affects them.

Common mistakes

Drawing the lithium level right after a dose.
Advising a low-salt diet or fluid restriction to a person on lithium without the prescriber.
Giving the next dose to a person with vomiting and diarrhoea without checking with the prescriber.
Treating a new rash on lamotrigine as minor.

Test yourself

Think of the answer, then tap the question to see it.

When is a lithium blood level usually drawn?

As ordered, usually 10–12 hours after the last dose, with the time of that dose recorded.

Which early signs suggest lithium toxicity?

Diarrhoea, vomiting, drowsiness, muscle weakness and lack of coordination. Hold the dose and notify the prescriber.

Why does dehydration matter for a person taking lithium?

Less fluid and salt raise the lithium level and can cause toxicity; vomiting, diarrhoea, sweating and fever are reported.

Which laboratory checks go with valproate?

Liver tests and platelets (and other tests the prescriber orders), because of the risk of liver damage, low platelets and pancreatitis.

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Connections

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Educational content for students; it does not replace your institution's protocols, supervised clinical training or a prescriber's order. Dose-calculation examples use made-up numbers: they are educational, not a clinical order.

Sources: Nursing: Mental Health and Community Concepts, 8.3: Treatments for bipolar disorders (Open RN, Wisconsin Technical College System (CC BY 4.0), LibreTexts, 2022); Nursing: Mental Health and Community Concepts, 6.4: Mood stabilizers (Open RN, Wisconsin Technical College System (CC BY 4.0), LibreTexts, 2022); mhGAP Intervention Guide for mental, neurological and substance use disorders in non-specialized health settings, version 2.0 (World Health Organization (WHO), 2016); Lithium (drug information) (MedlinePlus, U.S. National Library of Medicine, 2026).

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