Blood tests can be used to detect the presence of illegal, prescription and over-the-counter drugs in one's system. Such tests may be requested by law enforcement or employers as part of routine screening processes. Once a blood sample is collected, is it sent to a lab where a technician can determine which drugs are present. To learn more about how blood drug tests work, read our Blood Test Guide - Drugs and interviews with drug test experts Greg Johnson, Elina Smith and Mike Clark.
