You shouldnt have any worries. Usually they are just checking to see if your in good physical form. You would usually have to sign something for them to check for illict subtances. But it is for School.... SO if you're really NOT sure. You could quick smoking for a little bit and get lots of vitamin C and Water in your system like it was going out of style. Also, if you want to spend some money. Goto to local vitamin/health/GNC store and buy this big bottle of foul tasting juice. 50 Dollars. Its kinda steep, but it works. You drink it within an hour of testing and it cleans your body of everything. I can vouch for it. It works