Drug screening is commonly used by employers to test potential new employees for the presence of illegal drugs and alcohol. Drug screening is also commonly used on the job site when an accident occurs. Drug screening is done by taking a sample of hair, urine or blood and sending it to a testing lab to verify whether or not the sample contains illegal drugs or alcohol. Most illegal drugs stay in the body for at least 24 hours after use, and some can be detected up to a month after being used. Avoiding the use of illegal drugs and alcohol is a wise decision for any person seeking a new place of employment.
Marijuana is tested for in nearly all drug screenings. Infrequent use of marijuana can be detected by urine tests if it has been used within the last three to five days. Heavy use of marijuana can be detected as long as three to four weeks after the last use when urine testing is employed. Hair testing can detect any usage up to three months after use. Blood and saliva testing can only detect very recent use (within 24 hours) and are the least accurate measurements of use.
Cocaine is very commonly tested for in a drug screen. In urine, cocaine (including crack) can be detected two to five days after use. A blood- or saliva-based test can also detect use within the last five days. Hair testing is the most accurate test for cocaine, and can detect cocaine up to 90 days after the last usage.
Methamphetamine is now very commonly tested for in drug screens. Methamphetamine can be detected in a urine test three to five days after the last usage. A hair-based drug screen can detect use of methamphetamine up to 90 days after the last usage. Methamphetamine can be detected in the blood and saliva for up to three days after the last use.
Heroin is almost always tested for in a drug screen. Heroin can be detected in urine up to four days after the last use. In blood and saliva, heroin can be detected up to two days after the last use. A hair-based drug screen can detect use up to 90 days after the last usage.
Alcohol, although legal, is tested for in almost all drug screenings. Alcohol can be detected in the urine six to 24 hours after the last use. In a hair-based test, it can be detected for up to 90 days. In a blood- or saliva-based drug screen, alcohol can be detected for up to 24 hours after use.