Lithium is a highly effective mood stabiliser, and it is also a medicine where the gap between an effective level and a harmful one is narrow. That single fact explains almost everything about how it is used: the regular blood tests, the emphasis on fluid and salt, and the long list of things that can push levels up.
Knowing the signs of lithium toxicity is the most useful thing on this page. It is treatable when recognised early and dangerous when it is not.
Common side effects and early adjustment effects
- A fine tremor of the hands
- Increased thirst and passing more urine, including at night
- Nausea, stomach discomfort or loose stools, often early and often settling
- A metallic taste in the mouth
- Weight gain
- Mild swelling of the hands or feet, and acne or worsening psoriasis
A fine, steady tremor is common and not in itself alarming. A coarse tremor, one that is new, marked and clumsy rather than fine, is different and is a warning sign of toxicity.
Serious mood, behaviour or physical symptoms to take seriously
Lithium toxicity is a medical emergency. Get urgent help, and take your lithium with you, for:
- A coarse tremor, or new muscle twitching or jerking
- Vomiting, or severe or persistent diarrhoea
- Drowsiness, confusion, or slurred speech
- Unsteadiness on your feet, or difficulty walking
- Blurred vision or ringing in the ears
- Seizures
Toxicity is often triggered by something that concentrates lithium rather than by a dose change: dehydration, a vomiting or diarrhoea illness, hot weather with heavy sweating, a sudden drop in salt intake, or starting certain other medicines. See lithium toxicity symptoms.
Longer-term effects to monitor for: an underactive thyroid, which can present as tiredness, weight gain and feeling cold; reduced kidney concentrating ability, showing as increasing thirst and urination; and raised calcium. All are picked up on the routine blood tests, which is why the tests continue indefinitely.
Sexual, sleep, weight and emotional side effects
Weight gain is common and worth raising early, because it is easier to address before it becomes substantial. Some people report reduced sexual desire, and some describe feeling emotionally flattened or less creative. These are legitimate things to discuss rather than accept silently, as dose adjustment sometimes helps.
Increased night-time urination can disturb sleep. Mention it, since it may relate to how the dose is divided across the day.
Interactions, alcohol, pregnancy and other risk factors
Several very common medicines raise lithium levels. Check before starting anything new, including things bought without a prescription.
- Anti-inflammatories such as ibuprofen. A frequent cause of raised lithium levels. Paracetamol is usually preferred, but confirm with a pharmacist.
- Diuretics, particularly thiazides.
- ACE inhibitors and ARBs such as enalapril or losartan.
- Salt intake. Keep it steady. A sudden reduction, including from a new low-salt diet, can raise lithium levels.
- Fluids. Maintain steady intake, and take extra care in hot weather, during exercise, and during any illness with fever, vomiting or diarrhoea.
- Alcohol. Contributes to dehydration and affects mood stability.
Pregnancy. Lithium carries specific risks in pregnancy and needs specialist input rather than a decision made alone. Stopping abruptly also carries a high risk of relapse. Discuss well in advance of any planned pregnancy, and contact your team promptly if you become pregnant unexpectedly.
What to ask your doctor before changing dose or stopping
Never stop lithium abruptly. Doing so carries a substantial risk of relapse, and stopping is planned gradually when it is appropriate at all.
- When is my next lithium level due, and what was the last one?
- When were my thyroid, kidney and calcium last checked?
- What should I do if I get a vomiting or diarrhoea illness?
- Which painkillers can I use?
- Do I have a lithium record card, and should I carry it?
See lithium blood tests for what the monitoring involves.
Related mental health medication guides
- Mental health medication side effects
- Should I stop my mental health medication
- When to call a doctor
- Long-term mental health medication side effects
- Report a side effect in South Africa
See also mood stabiliser side effects and bipolar medication side effects.
Medical Disclaimer: This content is for informational and educational purposes only and does not constitute medical diagnosis, prescription, or professional advice. Always read the patient information leaflet and consult a qualified doctor or pharmacist regarding any medicine or health concern.