Generally, to get a menial job in America, you have to piss in a cup so a lab can make sure that you're not undermining the War On Some Drugs by putting a non-societally-approved drug into your body. Most effective when testing for marijuana, possibly the most innocuous of all drugs; a recreational dose of pot can be detected anywhere from one to six weeks after use, depending on how regularly you use it. Heroin, cocaine and LSD are generally undetectable within two days.