How often does lithium need to be monitored?

During the first year, check a 12-hour trough lithium level, kidney function (eGFR and electrolytes), calcium, and thyroid-stimulating hormone (TSH) at months 3, 6, 9, and 12. After the first year, if stable, every six months is appropriate for lithium level, eGFR, calcium, and TSH, with a full annual set (also including FBC, magnesium, fasting glucose, HbA1c, lipids, blood pressure, urinalysis, and ECG if cardiac risk) once per year. Any dose change requires a trough level five to seven days later. Illness, dehydration, or a new interacting medication warrants a level within 24–48 hours.

When is the blood test for lithium level timed?

The sample must be a 12-hour trough — drawn exactly 12 hours after the last dose, before the morning dose. Sampling at any other time overestimates or underestimates the true exposure. Ask the patient to delay their morning lithium until after the blood test. Write '12-h trough lithium level, last dose [time]' on the pathology request. Wait five to seven days after any dose change before checking the level, as this is the time needed to reach steady state. Non-trough sampling is one of the most common causes of avoidable toxicity and unnecessary dose adjustments.

Which medications interact dangerously with lithium?

The most important interactions raise serum lithium levels: regular non-steroidal anti-inflammatory drugs (NSAIDs including ibuprofen, naproxen, diclofenac, and celecoxib) increase lithium by 25–60% via prostaglandin-mediated renal vasoconstriction and must be avoided — paracetamol is the safe alternative for pain. ACE inhibitors and angiotensin-receptor blockers (ARBs) raise lithium by around 25%. Thiazide diuretics raise lithium by 25–40% and should generally be avoided. Metronidazole modestly raises levels. Caffeine withdrawal — for example, skipping coffee on holidays — can also spike the level. Theophylline lowers lithium by increasing renal excretion. Counsel patients to tell every prescriber and pharmacist they take lithium.

What happens to lithium levels during pregnancy?

Pregnancy substantially alters lithium pharmacokinetics. Blood volume increases during the second and third trimesters, diluting lithium and dropping levels — requiring dose increases to maintain efficacy. At delivery, blood volume drops sharply and lithium can spike rapidly, risking toxicity in the days after birth. Lithium monitoring should shift to fortnightly in the third trimester, then immediately after delivery. Lithium carries a small increased risk of Ebstein's anomaly (approximately 0.05% versus a background risk of 0.01%), and a fetal echocardiogram at 18 weeks is recommended. Pregnancy management is always specialist-led; stopping lithium in pregnancy carries a 50–70% relapse risk, so continuation is often appropriate with close monitoring.

What long-term organ effects does lithium cause?

Three long-term complications are most important to monitor. Chronic kidney disease develops in approximately 20% of long-term users over 20 years, with a slow progressive decline in eGFR — plot the trend at every visit and discuss switching with the psychiatrist if eGFR falls below 60 mL/min/1.73m² and is declining. Hypothyroidism occurs in 5–35% of people on long-term lithium — check TSH every six months and treat with thyroxine if needed without stopping lithium. Hypercalcaemia from lithium-induced hyperparathyroidism affects about 10% of long-term users — check calcium annually and refer to endocrinology if symptomatic. Nephrogenic diabetes insipidus (polyuria, polydipsia) affects around 30% but is usually mild.

Lithium monitoring

Lithium monitoring: GP guide to safe prescribing and shared care

By Dr HB Lo, FACRRM Reviewed 20 August 2026 10 min read

Lithium carbonate is the most evidence-based mood stabiliser for bipolar disorder and uniquely reduces suicide risk. Because it has a narrow therapeutic window — therapeutic 0.6–0.8 mmol/L for maintenance, toxic above 1.5 — blood levels, kidney function, and thyroid must be checked every three to six months.

In general practice, shared-care means maintaining the monitoring schedule, recognising early toxicity, counselling patients on sick-day rules and drug interactions, and coordinating with the psychiatrist for dose changes and long-term complications including chronic kidney disease, hypothyroidism, and hypercalcaemia.

Lithium carbonate is one of the oldest and most effective treatments in psychiatry. Discovered by John Cade in Melbourne in 1949, it remains the gold-standard mood stabiliser for bipolar disorder maintenance and the only mood stabiliser shown to independently reduce suicide risk — a property demonstrated in a 2013 meta-analysis of 48 randomised controlled trials by Cipriani and colleagues in the BMJ, showing approximately 60% reduction in all-cause mortality. For the GP managing bipolar disorder in shared care with a psychiatrist, lithium monitoring is a structured, high-stakes task: the therapeutic window is narrow, the consequences of toxicity are serious, and the long-term organ effects require systematic surveillance.

This page summarises the guideline-aligned approach to lithium shared-care in Australian general practice, following the RANZCP 2020 Mood Disorders Clinical Practice Guideline, Therapeutic Guidelines (eTG), and the Australian Medicines Handbook (AMH).

A. Core clinical: pharmacology, indications, and monitoring

What lithium does and who it is for

Lithium is a monovalent cation with multiple intracellular targets, including inositol monophosphatase and glycogen synthase kinase-3β. It is almost entirely renally excreted with no hepatic metabolism, giving it a half-life of 18–36 hours (longer in the elderly). The therapeutic window for maintenance is 0.6–0.8 mmol/L and for acute mania 0.8–1.0 mmol/L. The level becomes toxic above 1.5 mmol/L and severely toxic above 2.5 mmol/L. Steady state is reached five to seven days after any dose change.

In Australian practice, the primary indications are bipolar I and II maintenance (first-line per RANZCP 2020 and NICE CG185), acute mania (often combined with an atypical antipsychotic), and augmentation of antidepressant therapy in treatment-resistant unipolar depression.

Pre-lithium baseline investigations

Before initiating lithium, a full baseline is mandatory:

Renal: eGFR, creatinine, electrolytes (sodium, potassium, calcium, magnesium), urinalysis
Thyroid: TSH and free T4
Haematology: full blood count (lithium may cause a benign leukocytosis)
Metabolic: fasting glucose, HbA1c, lipid panel, weight, and BMI
Cardiac: ECG, particularly in patients over 40 years or with cardiac risk factors
Obstetric: pregnancy test in women of childbearing potential

The monitoring schedule

The most common error in lithium shared-care is non-trough sampling. The blood test must be drawn exactly 12 hours after the last dose, before the morning dose is taken. Non-trough sampling overestimates exposure and leads to unnecessary dose reductions. The pathology request should specify “12-hour trough lithium level” with the dose and time of last dose recorded.

After any dose change, wait five to seven days before checking the level. The structured monitoring schedule recommended by eTG and the AMH is:

Months 0, 3, 6, 9, 12: lithium level (trough) + eGFR + electrolytes + calcium + TSH + weight
From year two onward (stable): lithium level + eGFR + calcium + TSH + weight every six months
Annual full set: above plus FBC, magnesium, fasting glucose, HbA1c, lipids, blood pressure, urinalysis, ECG if cardiac risk, and PTH if calcium is elevated
After illness, dehydration, or new interacting medication: lithium level and renal function within 24–48 hours

Sick-day rules — patient counselling

Because lithium is renally excreted without any hepatic buffer, any state that reduces renal perfusion raises levels rapidly. The three dehydrating triggers that patients must understand are: vomiting or diarrhoea lasting more than 24 hours, high fever with inability to maintain oral intake, and heat exposure or strenuous exercise without adequate hydration. The instruction is simple: if you cannot keep fluids down for more than 24 hours, pause lithium and contact your GP the same day. If you develop coarse tremor, confusion, or unsteadiness, stop lithium immediately and go to the emergency department.

Patients should also be counselled to maintain a consistent sodium intake — a sudden low-sodium diet raises lithium levels significantly, as sodium and lithium compete for renal reabsorption — and to inform every prescriber and pharmacist that they take lithium.

B. Toxicity recognition and drug interactions

Recognising lithium toxicity

Lithium toxicity presents across a spectrum. Mild toxicity (level 1.5–2.0 mmol/L) produces worsening gastrointestinal symptoms, a coarse tremor replacing the usual fine postural tremor, polyuria, and mild lethargy. Moderate toxicity (2.0–2.5 mmol/L) adds dysarthria, marked ataxia, hyperreflexia, and fasciculations. Severe toxicity (above 2.5 mmol/L) causes confusion, delirium, myoclonus, seizures, cardiac arrhythmia, and renal failure — this is a medical emergency.

The distinction between a common side effect (fine postural tremor at a therapeutic level) and early toxicity (coarse tremor with any cognitive change or unsteadiness) is the most critical clinical decision in everyday lithium management.

Acute management: cease lithium; check serum lithium, U&E, calcium, ECG; start IV normal saline; refer to the emergency department. Haemodialysis is indicated for a level above 4 mmol/L regardless of symptoms, any level above 2.5 mmol/L with neurological or cardiac signs, renal failure with elevated lithium, or a persistently rising level after 24 hours of IV fluids.

Drug interactions — the most important ones for GP practice

Several drug classes commonly prescribed in general practice raise serum lithium by reducing renal clearance:

NSAIDs (ibuprofen, naproxen, diclofenac, celecoxib, mefenamic acid) raise lithium by 25–60% via prostaglandin-mediated afferent renal vasoconstriction. Regular NSAID use must be avoided; paracetamol is the appropriate alternative for pain. Low-dose aspirin (≤300 mg daily) is relatively safe.

ACE inhibitors and angiotensin-receptor blockers (ARBs) raise lithium by approximately 25%. If either class is needed for hypertension or heart failure, check the lithium level seven days after starting, again at one month, and then continue three-monthly monitoring.

Thiazide diuretics raise lithium by 25–40% and should generally be avoided. Loop diuretics also raise levels and require close monitoring. Metronidazole modestly raises lithium levels — usually safe for short courses but worth noting.

Caffeine increases renal lithium excretion — caffeine withdrawal (for example, stopping regular coffee intake during a holiday) can raise lithium levels. Counsel patients to maintain a consistent caffeine intake rather than abruptly stopping.

C. Long-term complications and maintenance management

Chronic kidney disease (~20% over 20 years)

Lithium causes a slow progressive decline in eGFR in a subset of long-term users. The key GP task is to plot eGFR over time at every visit — a declining trend is more significant than any single reading. Action thresholds: if eGFR falls more than 30% from baseline, discuss with the psychiatrist; if eGFR sustained below 60 mL/min/1.73m², raise the option of switching; consider switching strongly at eGFR below 45; and at eGFR below 30, switching is generally indicated unless the psychiatrist and nephrologist agree lithium is essential and unavoidable.

Lithium-induced nephropathy may be partly reversible if detected early. If lithium is continued in the setting of CKD, the target level should be lowered to 0.4–0.6 mmol/L, all nephrotoxic drugs must be avoided, and nephrology shared-care is appropriate.

Hypothyroidism (5–35%)

Lithium blocks thyroid hormone synthesis and release. Hypothyroidism is one of the most common long-term complications. Check TSH every six months. If hypothyroidism develops, treat with levothyroxine — typically starting at 50 µg daily and titrating to a TSH of 0.5–2.5 mIU/L. There is no need to stop lithium; hypothyroidism is treatable and lithium continuation is appropriate unless there are other reasons to reconsider.

Hypercalcaemia and hyperparathyroidism (~10%)

Lithium raises calcium by both direct effect and by increasing parathyroid hormone (PTH) secretion. Check calcium annually. If calcium is elevated, check PTH. Symptomatic hypercalcaemia — renal stones, fragility fractures, peptic ulcer disease, or significant psychiatric symptoms — warrants an endocrinology referral. Parathyroidectomy may be indicated in symptomatic cases.

Nephrogenic diabetes insipidus (~30%)

Approximately one in three long-term lithium users develops polyuria and polydipsia from nephrogenic diabetes insipidus. Most cases are mild. For significant polyuria, assess urine and serum osmolality. Management options include amiloride 5–10 mg daily (which counteracts lithium-induced aquaporin-2 dysregulation without raising lithium levels), or lithium dose reduction. Thiazide diuretics can reduce polyuria but raise lithium levels, making close monitoring essential if this approach is taken.

Formulation and dose

Quilonum SR 450 mg (slow-release) once daily at bedtime is the preferred maintenance formulation — it produces a smoother pharmacokinetic profile with reduced peak side effects and supports once-daily adherence. Standard lithium carbonate (Lithicarb 250 mg) is used for more granular dose titration. Both are available on the PBS without authority.

D. Australian operations

MBS item numbers for lithium monitoring visits

Standard monitoring visits are typically billed as MBS item 23 (short consultation) or item 36 when a new problem or dose change is addressed. Patients with bipolar disorder are eligible for a Mental Health Care Plan (item 2715 for preparation, item 2712 for review), providing access to up to 10 individual psychology sessions under Better Access per calendar year.

For patients with two or more chronic conditions, a GP Chronic Condition Management Plan (item 965 face-to-face preparation) and review (item 967) are appropriate — bipolar disorder on lithium qualifies. Practice nurses can facilitate lithium-level blood draws and routine monitoring visits via item 10997. Mental health telehealth items (video and phone variants of 2715/2712) have a standing exemption from the 12-month relationship requirement and are well-suited to stable lithium monitoring reviews.

Medico-legal considerations

Driving: Austroads Assessing Fitness to Drive 2022 indicates that acute manic, hypomanic, or severe depressive episodes make a person unfit to drive. Lithium at a therapeutic level with a stable mood state does not preclude driving; commercial vehicle standards are stricter.

SafeScript: Lithium itself is not a Schedule 8 monitored drug, but co-prescribed benzodiazepines, opioids, or stimulants must be checked via the real-time prescription monitoring system.

Suicide risk: Lithium-treated bipolar patients carry significant residual suicide risk. Screen at every visit; document your assessment. The suicide-protective effect of lithium is one reason to continue rather than switch at first sign of side effects.

E. Special populations

Elderly patients

In older adults, renal function declines with age, making lithium clearance slower and the margin for toxicity smaller. Start at a lower dose (125–250 mg daily), target a lower serum level (0.4–0.6 mmol/L), monitor renal function at least every three months, and be alert to interactions with antihypertensives. Falls risk from tremor and ataxia requires assessment. Cognitive effects may be more pronounced.

Pregnancy

Lithium management in pregnancy is always specialist-led. The congenital risk — approximately 0.05% Ebstein’s anomaly versus a background rate of 0.01% — is small relative to the 50–70% relapse risk if lithium is stopped. A fetal echocardiogram at 18 weeks is recommended. Lithium levels drop as blood volume expands in the second and third trimesters, requiring dose increases; levels spike immediately after delivery when blood volume falls rapidly. Check a lithium level within 48 hours of delivery. Women of childbearing potential should be counselled about pregnancy planning at initiation and at each annual review.

Breastfeeding

Lithium has a high relative infant dose (approximately 12–30%) and passes into breast milk. Breastfeeding while on lithium is a specialist-led decision. If the patient and specialist proceed, infant monitoring (serum level, thyroid, renal function) is required.

Renal impairment

If CKD is pre-existing, consider whether lithium is the right choice before initiating. If already established, monitor eGFR and lithium levels more frequently (at minimum every three months), target lower levels, avoid all nephrotoxic drugs, and coordinate with nephrology. RANZCP 2020 advises strongly considering a switch to an alternative mood stabiliser when eGFR falls below 45 mL/min/1.73m².

When to escalate

Urgency	Trigger	Action
Emergency	Coarse tremor + confusion, ataxia, dysarthria, or level ≥1.5 mmol/L with symptoms	Cease lithium. ED referral. IV fluids. Serum lithium, U&E, calcium, ECG. Call Poisons Information 13 11 26
Same-day	Vomiting/diarrhoea >24 h; cannot keep fluids down; fever with lithium use	Pause lithium. Check lithium level + eGFR. Oral rehydration if mild. Review in-person
Within the week	eGFR declining trend below 60; new calcium elevation; toxicity symptoms that resolved but level borderline	Psychiatry liaison; reassess indication and dose
Routine	Annual review; stable patient with new side effects; pregnancy planning discussion	Shared-care review with psychiatrist

Contact the Poisons Information Centre (13 11 26) for toxicity guidance. Haemodialysis indications are guided by the EXTRIP consensus 2015: level above 4 mmol/L, or above 2.5 mmol/L with neurological compromise, or renal failure, or slow clinical resolution.

For any patient in acute mental-health crisis or with suicidal thoughts: Lifeline 13 11 14 (24/7, text 0477 13 11 14), Suicide Call Back Service 1300 659 467, Beyond Blue 1300 22 4636, 13YARN 13 92 76 (First Nations), or 000 in an emergency.

What this article is and is not

This article is a clinical summary for Australian general practitioners supporting guideline-informed shared-care of patients established on lithium under specialist supervision. It reflects the RANZCP 2020 Mood Disorders CPG, eTG, and AMH at the time of authoring and may not reflect subsequent updates to national guidelines. It does not replace clinical judgement, specialist advice, or an individualised assessment of each patient’s circumstances. Individual patients may have features that require management differing from this overview. Always consult current primary references before prescribing or making clinical decisions.

Sources cited

Frequently asked questions

How often does lithium need to be monitored?

During the first year, check a 12-hour trough lithium level, kidney function (eGFR and electrolytes), calcium, and thyroid-stimulating hormone (TSH) at months 3, 6, 9, and 12. After the first year, if stable, every six months is appropriate for lithium level, eGFR, calcium, and TSH, with a full annual set (also including FBC, magnesium, fasting glucose, HbA1c, lipids, blood pressure, urinalysis, and ECG if cardiac risk) once per year. Any dose change requires a trough level five to seven days later. Illness, dehydration, or a new interacting medication warrants a level within 24–48 hours.
When is the blood test for lithium level timed?

The sample must be a 12-hour trough — drawn exactly 12 hours after the last dose, before the morning dose. Sampling at any other time overestimates or underestimates the true exposure. Ask the patient to delay their morning lithium until after the blood test. Write '12-h trough lithium level, last dose [time]' on the pathology request. Wait five to seven days after any dose change before checking the level, as this is the time needed to reach steady state. Non-trough sampling is one of the most common causes of avoidable toxicity and unnecessary dose adjustments.
What are the early warning signs of lithium toxicity?

Early signs of lithium toxicity (level 1.5–2.0 mmol/L) include worsening tremor (coarse rather than the usual fine postural tremor), nausea, vomiting, diarrhoea, lethargy, and mild unsteadiness. Moderate toxicity (2.0–2.5 mmol/L) adds dysarthria, marked ataxia, hyperreflexia, and fasciculations. Severe toxicity (above 2.5 mmol/L) causes confusion, delirium, seizures, and cardiac arrhythmia. Any patient with coarse tremor, confusion, or unsteadiness should be told to stop lithium immediately and attend an emergency department. A fine postural tremor without other features at a therapeutic level is a common side effect, not toxicity.
Which medications interact dangerously with lithium?

The most important interactions raise serum lithium levels: regular non-steroidal anti-inflammatory drugs (NSAIDs including ibuprofen, naproxen, diclofenac, and celecoxib) increase lithium by 25–60% via prostaglandin-mediated renal vasoconstriction and must be avoided — paracetamol is the safe alternative for pain. ACE inhibitors and angiotensin-receptor blockers (ARBs) raise lithium by around 25%. Thiazide diuretics raise lithium by 25–40% and should generally be avoided. Metronidazole modestly raises levels. Caffeine withdrawal — for example, skipping coffee on holidays — can also spike the level. Theophylline lowers lithium by increasing renal excretion. Counsel patients to tell every prescriber and pharmacist they take lithium.
What happens to lithium levels during pregnancy?

Pregnancy substantially alters lithium pharmacokinetics. Blood volume increases during the second and third trimesters, diluting lithium and dropping levels — requiring dose increases to maintain efficacy. At delivery, blood volume drops sharply and lithium can spike rapidly, risking toxicity in the days after birth. Lithium monitoring should shift to fortnightly in the third trimester, then immediately after delivery. Lithium carries a small increased risk of Ebstein's anomaly (approximately 0.05% versus a background risk of 0.01%), and a fetal echocardiogram at 18 weeks is recommended. Pregnancy management is always specialist-led; stopping lithium in pregnancy carries a 50–70% relapse risk, so continuation is often appropriate with close monitoring.
What long-term organ effects does lithium cause?

Three long-term complications are most important to monitor. Chronic kidney disease develops in approximately 20% of long-term users over 20 years, with a slow progressive decline in eGFR — plot the trend at every visit and discuss switching with the psychiatrist if eGFR falls below 60 mL/min/1.73m² and is declining. Hypothyroidism occurs in 5–35% of people on long-term lithium — check TSH every six months and treat with thyroxine if needed without stopping lithium. Hypercalcaemia from lithium-induced hyperparathyroidism affects about 10% of long-term users — check calcium annually and refer to endocrinology if symptomatic. Nephrogenic diabetes insipidus (polyuria, polydipsia) affects around 30% but is usually mild.

Source quality

Sources grouped by evidence tier. AU primary tier first; international where AU is silent or lagging; named-author reconstruction where guidelines have not yet caught up. How tiers work.

T1 AU primary 6 sources
T2 International primary 1 source
- NICE CG185 — Bipolar disorder: assessment and management
T3 Named-author reconstruction 4 sources
T4 Contrarian — examined 1 source
- PBS — lithium carbonate (Lithicarb / Quilonum SR)