I did too before.

If you google epilepsy and Lamictal, some people take like 600-800mg a day. I'm on 400 right now and took 800 once. No rash or OD here. (I googled this before when I was in your situation.)

FWIW, my pdoc said that it'd have to take repeated use of the double dose for me to be put at risk for "the rash", like at least 2-3 days in a row of the same 800mg for me. Not sure how much truth that is or isn't since I'm not a doctor... but I'm just forwarding what he told me. Obviously you'll need to call your pdoc like HALLIEBETH said