Drug screening is a test in which a tissue or fluid sample is analyzed to look for the presence of drugs. A number of drugs can be looked for in the sample, including illegal drugs as well as prescription drugs which are sometimes abused. This testing may be required for certain types of jobs, with people clearing a drug test when they start employment and are being subjected to random testing periodically. Refusal to undergo drug screening can mean denial of employment for job applications, and can result in suspension or termination for people already employed.
In addition to being used in the workplace, at both government and civilian jobs, drug screening is also used in a medical context. Hospitals may take a sample from a patient believed to be under the influence of drugs, or a patient who could be endangered by taking drugs and not informing hospital personnel. In this case, the test is performed because information about drug use could be relevant to medical treatment. Drug screening is also routinely performed as a part of some autopsies, in which case the technicians also look for traces of toxins and other unusual substances which might shed light on a death.
Oral swabs, blood, urine, and hair are all used for drug screening. The test can screen for the presence of drugs as well as their metabolites. Some labs will confirm positive results with the use of mass spectrometry, as false positives do happen, and taking the time to confirm can prevent confusion. The test results will indicate either that the blood contains no traces of drugs, or that traces have been detected, in which case the drugs will be identified.
It can take varying amounts of time for different drugs to show up in the body as they are metabolized. Drugs tend to show up in oral swabs most quickly, and linger in hair the longest. Urine tends to be used most frequently for drug testing, because it shows signs of recent drug use. Care must be taken when collecting samples to ensure that they are not contaminated. One problem with urine is that it is possible for the subject of the test to tamper with it, while something like a blood sample is harder to alter.
Several companies make drug screening kits which people can use to collect samples at home and send the samples in to a lab. These kits are often marketed at parents who are concerned that their children might be using drugs. Such kits are also sometimes used by workplaces that do not want to contract with a local lab.