I forgot to take mine too I found this answer in another thread:
"The mealtime dosing schedule (one hour before, during, or one hour after a meal) makes it easy to remember alli capsules. To help you remember, we recommend making alli a part of your pre-meal routine. Once alli and the routine have been paired several times, the association will become automatic. However, if a dose is missed, alli can be taken up to one hour after a meal and still be effective. The alli Shuttle™ carrying case is provided with the alli starter pack to enhance compliance and serve as a helpful reminder to take alli capsules with your meals."
SOURCES: http://myalli.com/whatisalli/commonquestions/useAndDosage.aspx