Lithium — Bipolar Disorder Medication Guide | KiwiMeds
✅ Reviewed by a Registered Pharmacist NZ | Last updated: May 2026 | This information is for educational purposes only and does not replace advice from your doctor or pharmacist.
What is lithium?
Lithium is a mood stabiliser used primarily to treat bipolar disorder. It reduces the frequency and severity of manic and depressive episodes. It has been used in psychiatry for over 70 years and remains one of the most effective treatments for bipolar disorder. In NZ it is available as lithium carbonate.
What is it used for? (NZ context)
Lithium is used to treat and prevent manic episodes in bipolar disorder, and as augmentation for treatment-resistant depression. It is funded by Pharmac in New Zealand. Because of its narrow therapeutic window, regular blood level monitoring is essential.
How does it work?
The exact mechanism of lithium is not fully understood, but it modulates several neurotransmitter systems (serotonin, dopamine, glutamate) and intracellular signalling pathways. It stabilises mood by reducing both the highs (mania) and lows (depression) over time.
How to take it
Lithium is taken 2–3 times daily with food to reduce stomach upset. Consistent fluid intake is crucial — dehydration increases lithium toxicity risk. Regular blood tests (lithium level, kidney and thyroid function) are essential. Do NOT reduce fluid intake significantly (e.g., on hot days, during exercise, or illness) without awareness of increased lithium levels.
Common side effects
- Tremor (fine hand tremor)
- Increased thirst and urination
- Weight gain
- Thyroid problems (hypothyroidism)
- Mild nausea
- Memory and concentration problems
Serious side effects to watch for
Lithium toxicity is a medical emergency. Signs include coarse tremor, confusion, slurred speech, vomiting, and seizures. Seek emergency help immediately. Toxicity occurs when lithium levels go above the therapeutic range — this can be triggered by dehydration, salt restriction, kidney problems, or interactions. Your doctor will regularly monitor lithium blood levels.
Important drug interactions
NSAIDs (ibuprofen, naproxen) — reduce kidney lithium clearance, raising levels to toxic range — use paracetamol instead. ACE inhibitors and diuretics — can also raise lithium levels dangerously. Salt restriction — reduces lithium excretion. Many other medications require careful monitoring.
NZ-specific information
Pharmac funding: Lithium carbonate 250mg and 400mg slow-release tablets are funded by Pharmac for bipolar disorder management.
Frequently asked questions
Why do I need blood tests on lithium?
Lithium has a narrow therapeutic window — the effective dose is close to the toxic dose. Regular blood tests (every 3–6 months when stable) ensure your level is in the safe range. Levels should ideally be checked 12 hours after your last dose.
Can I take ibuprofen if I’m on lithium?
No — ibuprofen and other NSAIDs reduce lithium excretion by the kidneys, causing lithium levels to rise to potentially toxic levels. Always use paracetamol for pain and fever instead. Tell your pharmacist you are on lithium whenever you buy any over-the-counter medicine.
Does lithium affect the thyroid?
Yes — lithium can cause hypothyroidism (underactive thyroid) in some people, especially with long-term use. Your doctor will monitor thyroid function tests regularly. If you develop symptoms of hypothyroidism (tiredness, weight gain, cold intolerance), report them.
💬 Talk to your pharmacist or doctor for personalised advice about lithium.
Reviewed by a Registered Pharmacist NZ | BPharm, Pharmacy Council of New Zealand
References & Further Information
The following New Zealand and international resources were used to inform this page: