Lithium is the GP's core share-care responsibility. Check the level 12 hours after the last dose, every time — regular monitoring is what keeps a uniquely effective drug safe.
Therapeutic levels
- Maintenance: 0.6–0.8 mmol/L — the target range to maximise relapse prevention.
- Acute mania: up to 0.6–1.0 mmol/L as tolerated, then back to the maintenance range once stable.
- Depression augmentation: 0.4–0.8 mmol/L when lithium is added to an antidepressant for treatment-resistant depression.
- Toxicity: symptoms commonly emerge above 1.5 mmol/L — the level alone doesn't reliably predict toxicity, so always correlate with the clinical picture.
Monitoring schedule
- Early maintenance: baseline, then 7, 14 and 28 days after starting or any dose change.
- Once stable: 3, 6 and 12 months, then annually if levels and renal/thyroid function stay stable.
- Recheck sooner: any change in presentation, an abnormal result, a new interacting medicine, or intercurrent illness.
Routine bloods (6-12 monthly)
- Renal: lithium level, electrolytes, urea, creatinine and eGFR — lithium can cause nephrogenic diabetes insipidus and, rarely, chronic kidney disease.
- Thyroid & parathyroid: TSH and calcium — both hypothyroidism and hyperparathyroidism are recognised long-term effects.
- Cardiometabolic: FBC, glucose, lipids, weight/BMI and a baseline ECG, repeated periodically.
Toxicity triggers. Dehydration, febrile illness, vomiting or diarrhoea (volume loss raises the level); NSAIDs (regular use more than occasional — reduces renal lithium clearance); ACE inhibitors or angiotensin receptor blockers (both can significantly raise the level); thiazide diuretics especially — consider amiloride instead if a diuretic is needed; any new or stopped interacting medicine, or major surgery — recheck around the time of the change.
Safety
- Always measure the level 12 hours after the last dose — an early or late sample makes the result uninterpretable.
- Recheck the level after starting or stopping an NSAID, ACE inhibitor, ARB or diuretic, and during any acute illness with vomiting, diarrhoea or reduced fluid intake.
- Don't rely on the level alone to exclude toxicity — symptoms can occur at normal or therapeutic concentrations, especially in older patients.
Red flags / refer
- Symptoms of toxicity (coarse tremor, ataxia, confusion, vomiting) → same-day medical assessment; measure the level urgently and consider hospital referral.
- Declining renal function or a thyroid/parathyroid abnormality on long-term lithium → nephrology or endocrinology review alongside continued psychiatric care.
- Planning pregnancy, or pregnant, while on lithium or valproate → specialist preconception review before any dose change.
MH-02B v1.0 · Reviewed Jun 2026 · Review Jun 2027
For health-professional use. Framework: RANZCP Mood Disorders CPG (2020); lithium interactions, Aust Prescr 2020;43:91-3. Companion sheet: MH-02A Recognition & Treatment.
