Drug and alcohol misuse is widespread throughout society at all levels and throughout the world although the patterns of use, the substances involved and the cultural attitudes may vary. However the effects on human performance and behaviour are well established and can have significant impact on the workplace, educational establishment or social setting.

According to the Office for National Statistics an estimated 1 in 11 adults aged 16 to 59 years had taken a drug in the last year (rising to 1 in 5 aged 16 to 24), and over 40% of these may have used a Class A drug. Cannabis is the most frequent drug used, followed by cocaine, although there continues to be significant use of ecstasy powder, new psychoactive substances with nitrous oxide continuing to be a problem in young people. However there are a wide variety of potential drugs of misuse, which can include medications otherwise available on prescription.

Drug misuse in the workplace has been shown to have a significant impact on attendance and employers have reported an effect on performance as well as potentially causing damage to businesses and accidents at work.

One of the tools available to combat drug misuse at work and in certain societal settings is testing. In recent years, point of use tests have become available which using urine or saliva can indicate the presence of illegal drugs in the body above a set threshold. Although accurate these tests have limitations and a non negative result should normally be followed by definitive laboratory testing and review by a trained Medical Review Officer who can discount any positive results from prescribed medication. Urine testing is more difficult to carry out but can pick up a wider window of use, whereas saliva testing only identifies those drugs present in the blood at the time although this is likely to be a better indicator of any effect on performance or behaviour. The testing regime in the kits is usually adapted to include those drugs in common use in a particular setting or society. Testing programmes can include pre-employment, random testing, for cause testing (post incident or behavioural) or as part of a treatment / monitoring programme,

Employers may wish to carry out drug testing for a variety of reasons which can include to mitigate health and safety risks, to promote employee health, potentially limit employee absence, to respond consistently to drug related disciplinary offences, protect organisational reputation / poor decision making and potentially to enhance employee performance. There are also certain settings where illegal drug use may have significant security implications. Regular testing does have a significant deterrent effect on the population being tested. Drug testing must be viewed as an element of a comprehensive drug and alcohol policy which identifies clearly why and how the testing is being carried out, and what will happen with the results,. Clear and informed consent must be obtained from being tested. In the UK there is specific guidance on this subject from the Information Commissioner.