I had to go off of Lamictal for a few days and was told by my doc that anymore than 5 days and you have to start at the lower dose and slowly work up to the therapeutic dosage. You have to slowly build up the drug in your system just like you did the first time or the chance of getting severe side effects, such as the rash, is greatly increased. I'm sure there are other reasons, but the increased chance of that rash was enough for me.

Talk to your doc if you aren't sure what to do. Be very careful and check for the rash everyday including the whites of your eyes, the eyelids, your gums, the insides of your cheeks, and watch out for burning urination (I don't know if you know that the rash can develop at the opening of the urethra and not be visible). It is always better to be safe than sorry.