Lamotrigine causes side effects in a significant number of people who take it, with dizziness, headache, and nausea being the most common. In clinical trials, dizziness affected about 38% of patients, headache about 29%, and nausea roughly 19%. Most side effects are mild and tend to improve as your body adjusts, but a few rare reactions require immediate attention.
The Most Common Side Effects
The side effects that show up most often, affecting at least 10% of patients in clinical trials, are dizziness, headache, double vision, drowsiness, unsteady coordination (ataxia), nausea, and general weakness. Dizziness is by far the most frequent, reported nearly three times more often in people taking lamotrigine than in those on a placebo. Headache runs a close second, though it’s worth noting that about 19% of placebo patients also reported headaches, so the drug itself may only account for part of that number.
Double vision and blurred vision are common enough that they can interfere with driving or reading, particularly when starting the medication or increasing the dose. Drowsiness tends to be most noticeable in the first few weeks. These effects often lessen over time, but if they persist or get worse, a dose adjustment can help.
Movement and Coordination Problems
Lamotrigine can affect motor control more than many people expect. Ataxia, a loss of smooth coordination that makes walking or fine motor tasks feel clumsy, occurs in roughly 22% of patients. Tremor shows up in about 4%, and speech difficulties in about 3%. These effects are dose-related, meaning they’re more likely at higher doses and often improve if the dose is reduced.
Skin Rashes and When to Take Them Seriously
Roughly 8% of people taking lamotrigine develop some kind of skin reaction, and while most rashes are benign, a small fraction are dangerous. Stevens-Johnson syndrome and toxic epidermal necrolysis, conditions where the skin blisters and peels off in sheets, occur in about 1 in every 2,500 people treated. These reactions are rare but potentially fatal, and they almost always develop within the first eight weeks of starting the drug.
This is the main reason lamotrigine is started at a very low dose and increased slowly over several weeks. A typical schedule begins at 25 mg per day for the first two weeks, increases to 50 mg in weeks three and four, then continues stepping up to a maintenance dose by week five or six. Skipping this gradual ramp-up, or restarting at a full dose after a break, significantly raises the risk of a serious skin reaction. If you take valproate alongside lamotrigine, the starting doses are even lower because valproate slows the breakdown of lamotrigine in your body.
Any new rash during the first two months of treatment deserves prompt medical evaluation. Warning signs of a dangerous reaction include a rash accompanied by fever, mouth sores, swollen lymph nodes, or blistering skin.
Mood Changes and Suicidal Thinking
The FDA requires a warning on all antiepileptic drugs, including lamotrigine, about an increased risk of suicidal thoughts and behavior. A pooled analysis of 199 placebo-controlled trials across 11 different antiepileptic drugs found that patients on these medications had roughly twice the risk of suicidal thinking compared to those on placebo. In concrete terms, about 0.43% of treated patients experienced suicidal ideation versus 0.24% on placebo, an increase of approximately one additional case for every 530 patients treated.
This is a class-wide effect, not unique to lamotrigine, and lamotrigine is actually prescribed as a mood stabilizer for bipolar disorder precisely because it helps prevent depressive episodes. Still, new or worsening mood symptoms, especially in the early weeks, are worth reporting to your prescriber.
Interactions With Hormonal Birth Control
Estrogen-containing birth control pills roughly double the rate at which your body clears lamotrigine. This means that during the weeks you take active pills, lamotrigine levels in your blood can drop by about half, potentially reducing its effectiveness. During the placebo week of your pill pack, levels bounce back up, creating a roller coaster that can trigger both breakthrough seizures and side effects in an alternating pattern.
If you use hormonal contraception, your prescriber will likely need to adjust your lamotrigine dose or suggest a non-estrogen contraceptive method. This interaction is specific to estrogen-containing formulations, so progestin-only options generally don’t cause the same problem.
Rare Immune System Reactions
A small number of patients have developed a severe immune overreaction called hemophagocytic lymphohistiocytosis (HLH) shortly after starting lamotrigine. The FDA identified eight cases in a surveillance report. In this condition, the immune system becomes hyperactivated and begins attacking the body’s own blood cells, causing high fever, enlarged liver or spleen, and abnormal blood counts. The cases reported improved after lamotrigine was stopped. HLH is extremely rare, but unexplained high fever combined with feeling very unwell in the early weeks of treatment should be evaluated urgently.
Long-Term Effects on Bone Health
One common concern with long-term use of antiepileptic drugs is bone thinning, which can raise fracture risk over years or decades. Lamotrigine appears to be one of the safer options in this regard. A two-year study of adults newly started on epilepsy medications found that lamotrigine did not reduce bone mineral density in the spine or hip, and it did not alter markers of bone turnover. This sets it apart from some older antiepileptic drugs that are known to weaken bones over time.
What Happens If You Stop Suddenly
Stopping lamotrigine abruptly can cause withdrawal symptoms including anxiety, mood swings, irritability, headaches, dizziness, fatigue, and nausea. For people taking it for epilepsy, the biggest risk of sudden discontinuation is rebound seizures, which can be more severe than the seizures the medication was controlling. Rebound depression and, in some cases, suicidal thoughts have also been reported after rapid withdrawal.
Standard guidance recommends tapering the dose over at least two weeks, typically reducing by about half each week. Many clinicians prefer a slower taper, cutting by 5% to 10% every one to two weeks, especially for people who have been on the drug for a long time or who are sensitive to dose changes. If you need to stop lamotrigine for any reason, work with your prescriber on a gradual schedule rather than discontinuing on your own.