How are drugs tested for?

Testing people

Drug testing is becoming more widespread in industry and in sport. Some schools, particularly public schools, have begun drug testing their students. And now some companies are advertising drug testing kits which parents can buy.

There are different types of tests. The most commonly used method is to test a sample of urine. Saliva or blood tests detect drugs that have been taken over the last 24 hours. Blood tests are expensive and invasive, so are rarely done. A urine test shows a history for most drug groups of between 1 to 4 days. To test if someone is ‘under the influence’ then a urine or saliva test is appropriate.

Traces of most drug groups disappear quickly in blood, saliva and urine, yet remain trapped in hair as a permanent record. Hair analysis typically provides a profile of drug use for between one week and up to 3 months or more. For evidence of a history of drug use or abstinence, say, in pre-employment tests or for assessing progress in the treatment of addiction, then a hair test is required. Hair tests are more technically difficult to do and are probably not as reliable as urine testing unless done in a competent laboratory.

Hair testing shows drug use history. Drugs have to be ingested over a period of time and taken at least three or four times for use to register. Second hand or atmospheric smoke do not alter the results(1).

For urine tests the approximate detection periods are:

Alcohol 12 – 24 hours
Amphetamine 2 – 3 days
Buprenorphine 2 – 3 days Cannabis 2 – 7 days but up to one month for regular users
Cocaine 12 hours – 3 days
Diazepam 1 – 2 days
Ecstasy 2 – 4 days
Heroin 1 – 2 days
LSD 2 – 3 days
Methadone 2 days
Temazepam 1 – 2 days (longer after injecting)

The results – particularly from home testing kits – are not always accurate. There can be false positives (a positive result where there is no drug use) and false negatives (a negative result where there has been drug use). If medicines have been taken they may give a positive test. For example, some cold remedies and cough syrups could produce positive results for opioids and/or amphetamines.

Testing drugs

The other type of drug testing is testing drugs, either to check for purity or contamination. A number of kits are available that dilute the drug and indicate by way of hue and how this relates to a chart, what the drug contains. These kits are useful for indicating that a drug contains dangerous chemicals or drugs not wanted. Some pressure groups in the UK  have set up drug testing stalls at parties and clubs to allow users to have a better idea of what they are taking, as is currently the practice in some Dutch clubs. ‘The Loop’ is an organisation that performs drugs testing allowing them access to useful information and trends on drug purity and ‘imposter drugs’, examples of their recent findings (post pandemic) can be found in this Volteface article. However, as well as legality problems – handing the drug over for testing and giving it back can be regarded as supplying the drug – most tests do not indicate how strong the drug is nor whether there are more than one type of drug found in the specimen.

Bristol now has the UK’s first regular drug checking service, delivered by non-profit The Loop in partnership with Bristol City Council. People can take substances for analysis to check content and strength. The service also offers consultations from health professionals. 

Testing for spiked drinks

Drug Rape is a crime that has risen in the last few years. Drugs like GHB or Rohypnol can be used to spike drinks. Recently companies have started to sell products which will test for the Benzodiazepines group of drugs, which are commonly associated with Drug Rape. These usually take the form of test strips or beer mats, which can be easily carried on a night out for discrete testing. They can also detect benzodiazepines in urine, and can be used as a ‘morning after’ test.

Updated January 2024