Most mood stabilizers used to help treat bipolar disorder are known to cause weight gain. However, Lamictal is less likely to cause weight gain.

Lamictal is a brand name for the drug lamotrigine. It’s an anticonvulsant and a mood stabilizer. As an anticonvulsant, it helps treat seizures. As a mood stabilizer, it helps lengthen the time between extreme mood episodes in bipolar disorder.

It’s used for long-term treatment of the more severe type of bipolar disorder, called bipolar I disorder. It’s also only used to treat bipolar I disorder in people who are 18 years and older who have already been treated with other medication for mood episodes.

Most mood stabilizers used to treat bipolar disorder are known to cause weight gain. The way a mood stabilizer affects your weight depends on many things, such as how severe your disorder is and what other conditions you have.

Unlike most mood stabilizers, though, Lamictal is less likely to cause weight gain. In clinical trials, less than 5 percent of those taking Lamictal gained weight. If you take Lamictal and have gained weight, the weight gain may be an effect of the disorder itself.

Bipolar disorder can increase your appetite or change your metabolism. These changes can lead to weight gain, making it difficult to tell what the actual cause may be.

Continued changes in mood from bipolar disorder can affect your motivation to exercise or follow a healthy meal plan.

If you’re concerned about weight gain during your treatment for bipolar disorder, your doctor can refer you to a nutritionist. Working with a nutritionist can help you maintain a healthy weight.

Continued changes in mood can not only affect your weight but may also be a sign that the drug you’re taking isn’t working as well as it should be. If you have continued changes in mood during therapy for bipolar disorder, tell your doctor.

A mood stabilizer’s effectiveness differs from person to person. You may need to try different medications before you find one that works for you. However, you should never stop taking your bipolar disorder medication without first talking to your doctor.

If weight gain is a concern for you during your bipolar disorder treatment, discuss Lamictal with your doctor. Although Lamictal is less likely to cause weight gain, it can cause other side effects and interactions.

Below is more information you should consider if you take this drug or plan to take this drug.

More common side effects

The more common side effects of Lamictal in people treated for bipolar I disorder include:

  • nausea
  • sleeping trouble
  • sleepiness or extreme tiredness
  • back pain
  • rash
  • runny nose
  • stomach pain
  • dry mouth

Serious side effects

Serious skin rashes

These rashes may need treatment in a hospital. They can also be fatal. This side effect can happen at any time, but it’s more likely to happen within the first 8 weeks of treatment. Symptoms can include:

  • rash
  • blistering or peeling of your skin
  • hives
  • painful sores in your mouth or around your eyes

Reactions that can affect the function of your liver or blood cells

Symptoms of these reactions can include:

  • fever
  • frequent infections
  • severe muscle pain
  • swollen lymph glands
  • unusual bruising or bleeding
  • weakness or tiredness
  • yellowing of your skin or the whites of your eyes
  • swelling of your face, eyes, lips, or tongue

Suicidal thoughts or actions

Aseptic meningitis

This is inflammation of the protective membrane that covers your brain and spinal cord. Symptoms can include:

  • headache
  • fever
  • nausea
  • vomiting
  • stiff neck
  • rash
  • unusual sensitivity to light
  • muscle pains
  • chills
  • confusion
  • drowsiness


If you take Lamictal with certain drugs, the interaction may cause side effects. Interactions may also cause one or more of the drugs to stop working normally.

Taking the anticonvulsant and mood-stabilizing drugs valproic acid or divalproex sodium (Depakene, Depakote) along with Lamictal can double the amount of Lamictal that stays in your body. This effect can greatly increase your chances of side effects from Lamictal.

On the other hand, taking the anticonvulsant and mood-stabilizing drugs carbamazepine (Tegretol), phenytoin (Dilantin), phenobarbital (Luminal), or primidone (Mysoline) along with Lamictal can decrease the levels of Lamictal in your body by about 40 percent.

Estrogen-containing birth control pills and the antibiotic rifampin (Rifadin) also can decrease Lamictal levels by about 50 percent. These effects can greatly reduce how well Lamictal works to treat your symptoms of bipolar disorder.

Other conditions

If you have moderate liver or kidney damage, your body may not process Lamictal as well as it should. Your doctor may suggest a lower starting dosage or a different drug.

Pregnancy and breastfeeding

It’s not known if Lamictal is safe to use during pregnancy. Tell your doctor if you’re pregnant or plan to become pregnant before taking this drug.

Lamictal also passes into breast milk and may cause side effects in your child if you breastfeed. Talk to your doctor about the best way to feed your child if you take Lamictal.

Finding a drug that works well to treat your bipolar disorder that also causes the fewest side effects can be a challenge. If Lamictal is not the right drug for you and weight gain is a concern, talk to your doctor.

Most other drugs for bipolar disorder do cause weight gain. Your doctor may suggest healthy foods, exercises, or other techniques that could help you minimize weight gain.