In young adults who are taking carbamazepine (Tegretol, Tegretol XR, Carbatrol), phenytoin (Dilantin, Phenytek), phenobarbital, or primidone (Mysoline), but NOT valproate (Depakote, Depakene, or valproic acid), Lamictal is usually started at 25 milligrams (mg) twice a day. Every week or two, the amount can be increased by 50 mg per day if needed to control seizures (if side effects are not troublesome), to a target dose of 300-500 mg per day.

Adults who do take valproate (Depakote, Depakene, or valproic acid) may start by taking 12.5 to 25 mg of Lamictal every other day, with increases of 25 mg every two weeks. The target dose is usually 150 to 200 mg daily, in one or two doses.

When Lamictal is used alone (that is, as monotherapy), the starting dose is 25 mg a day, increased by 25 mg daily every two weeks as needed, usually to 100 to 200 mg a day.

Patients over age 65 generally require a lower initial dose and lower target maintenance dose.

The doctor occasionally may suggest checking the level of Lamictal in the blood to see whether it falls within the range that is usually considered appropriate for treatment ("therapeutic level"). Whether the amount prescribed needs to be adjusted generally depends on whether seizures or side effects are occurring, however.