Lamotrigine is used in epilepsy and as a mood stabiliser in bipolar disorder. Most people tolerate it well, and it avoids some of the weight and sedation effects of alternatives.
One warning matters more than everything else on this page: report any rash immediately, particularly in the first eight weeks of treatment or after a dose increase. Lamotrigine can rarely cause a severe skin reaction that becomes life-threatening. Most rashes on lamotrigine turn out to be harmless, but they cannot be told apart at home, so the rule is to seek advice the same day rather than watch and wait.
This is also why the dose is increased slowly over weeks when starting. The slow build-up substantially reduces the risk, so do not increase faster than instructed, and tell your prescriber if you have missed several days, because restarting may need to begin again at a low dose.
Common side effects and early adjustment effects
- Headache
- Dizziness or unsteadiness
- Double or blurred vision, particularly at higher doses
- Nausea
- Drowsiness, or difficulty sleeping
- Tremor
- Irritability
These are often dose-related and frequently ease as treatment settles. Lamotrigine is generally weight-neutral, which is one reason it is chosen over some alternatives.
Serious mood, behaviour or physical symptoms to take seriously
Get urgent medical help for any rash, and immediately for a rash that:
- Blisters or peels
- Involves the mouth, eyes, or genitals
- Comes with fever, sore throat, swollen glands or feeling generally unwell
- Is spreading quickly, or comes with facial swelling
See medicines causing a blistering rash and drug rash.
Also seek urgent help for: a high fever with swollen glands and feeling very unwell, which can indicate a serious hypersensitivity reaction; unexplained bruising or bleeding, or repeated infections; yellowing of the eyes or skin; and new or worsening thoughts of self-harm, which need urgent contact regardless of the medicine.
Report worsening seizure frequency or a change in seizure type.
Sexual, sleep, weight and emotional side effects
Lamotrigine is generally less associated with weight gain, sedation and sexual side effects than several alternatives in both epilepsy and bipolar treatment, which is often part of the reason it is selected.
Sleep can be affected in either direction, and some people report irritability or mood changes. Both are worth reporting, since dose timing or amount can sometimes be adjusted.
Interactions, alcohol, pregnancy and other risk factors
Lamotrigine has two interactions that change the dose substantially, and both are easy to overlook:
- Sodium valproate. Raises lamotrigine levels considerably, so a much lower lamotrigine dose and an even slower increase are needed when they are combined. See sodium valproate side effects.
- Hormonal contraceptives. Some can lower lamotrigine levels, and starting or stopping one can change how well it works. This includes the pill. Tell your prescriber before any change to contraception. See hormonal contraception side effects.
- Other epilepsy medicines. Several affect lamotrigine levels in both directions.
- Alcohol. Adds to dizziness and drowsiness.
Pregnancy. Lamotrigine requirements often change during pregnancy and levels may need monitoring. Any epilepsy or bipolar medicine in pregnancy needs specialist input, planned in advance where possible. Do not stop on discovering a pregnancy without urgent advice. See mental health medication in pregnancy.
What to ask your doctor before changing dose or stopping
Never stop this medicine abruptly. If it is being taken for epilepsy, sudden withdrawal can trigger seizures, including prolonged seizures that are themselves dangerous. If it is being taken for mood stabilisation, stopping suddenly carries a high risk of relapse. Any reduction is planned with your prescriber.
- What exactly should I do if I develop a rash?
- What should I do if I miss doses for several days?
- Does my contraception affect this medicine?
- What is my dose increase schedule, and why that pace?
- What should I know if I am planning a pregnancy?
Related mental health medication guides
- Mood stabiliser side effects
- Epilepsy medication side effects
- Bipolar medication side effects
- Should I stop my mental health medication
- Report a side effect in South Africa
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.