You should test when you think someone might be abusing drugs; we call this reasonable suspicion test.\rTest randomly at least once a week or twice a week for the first month.\rNever give prior notice until you are sure they are clean.\rEmployers will often test new hires, after an accident (post-accident) if they suspect abuse in the workplace (reasonable suspicion).\rParents use them when they suspect there is a problem with their teen’s attitude, or they find drugs in the home.