One test kit can screen for THC metabolites, cocaine, amphetamines, PCP, opiates and other substances. This test is very accurate, detecting the exact number of molecules as well as their concentration levels. Of course, if you are a heavy and regular smoker, your chances of getting caught increase dramatically. Your body fat becomes loaded with THC, and a urine test can be positive for up to six weeks after you stop smoking pot. By contrast, if you are a casual user, most preliminary urine screening tests will pick up a single joint smoked within one to three days of the test.
People go to all sorts of trouble to defeat drug tests.
In fact, we have a list of more than 50 products that promise to help you do that. You would be amazed at what people are selling. Most tests are supervised, so that usually won't work. Most drug testers now test for the adulterants too. The products that supposedly cleanse and flush are simply diuretics.