I take 200 MG of Lamictal in the morning and 400 in the evening. It has never had an effect on my sleep. Once, when I was a teenager and I stopped taking my meds, I restarted it (full dose) all at once and it gave me vertigo so badly I had to go by ambulance to the hospital. I'm sure that is a rare side effect but I would advise anyone not to start on a high dose (there are reasons they titrate some meds). Also, I am terrible at my morning meds. I take them between 9 and 12:30. I take my evening meds at 9PM.