If you are dirty, go to your local health food store, and buy quick tabs, or something like that and follow the instructions exactly. They usually require that you drink a lot of water, as this will dilute your urine, and the tabs will mask the chemicals that they test for. Usually the pills or tabs will cost you about 35 bucks, but make sure you buy ones that have a money back guarantee. The tabs don't always work, especially if you use them often.