Cansford Labs guidelines for drug testing in the workplace – Part 1

Which policy?

An increasing number of companies in the UK are utilising drug testing as a tool to address the potential health and safety and performance issues  that drug use by employees and job candidates present.

Workplace drug testing can have a deterrent effect on existing employees and can be used to screen new employees.

The use of drug testing in the Workplace requires a clear, written policy that is discussed and agreed with all employees before testing starts. One of the main questions you will face is “what will you do when people test positive?” This process not only needs to be written up in your company policies and procedures.

Random drug tests for existing employees

The main use of drug testing in the workplace is to be confident that people are fit to perform specific tasks and ensure that no drugs are present in the person’s system that may impair performance or put others at risk. These tests are usually performed randomly. Whilst these tests do not accurately reflect or predict fitness to work, they do detect recent drug use when the test is positive.

Urine test is the most commonly used sample for illicit drugs. It detects the use of drugs within the last few days and as such is evidence of recent use; but a positive test does not necessarily mean that the individual’s performance was impaired at the time of the test.

The use of saliva (oral fluid) is ideal in such cases, when drugs are present in saliva samples, they actually reflect the use of drugs in the last 24 hours and so are very relevant in assessing impairment.

Pre-employment drug tests for job applicants

For some industries it is important to have the assurance that a job applicant is not a regular user of drugs.

In these cases testing a 3-centimetre head hair sample covering a period of three months is ideal because the candidate will have to abstain from drugs for 3 months for the test to be negative.

Most industries, however, still require a negative urine drug screen test as a condition for employment.  This can only provide a 3 to 5 day window of detection at maximum and if the candidate is pre-warned of the test, the candidate can abstain before the test, making the test useless.

A sample of hair covering a period of approximately three months is equivalent to 20 urine tests in the length of coverage it provides.

Oral fluid, urine or hair?

Employers face a difficult task to choose the best sample to use in drug testing that suits best for their needs. The three common samples – urine, saliva and hair – each have different advantages depending on the purpose of the test and they can be complementary in different situations. There is not a best sample for drug analysis, just the ideal sample for a particular purpose.BlueMan

Drug testing in urine and saliva (or oral fluid) reflects drug use on a relatively short period before sample collection (24–72 h) depending on the drug, but it cannot detect impairment. Abstention from use for 3 days will often produce a negative urine test result.

Oral Fluid or Saliva is easy to collect. Drugs remain in oral fluid for a similar time as in blood and its use is a good way of detecting actual current drug use and is more likely to reflect impairment.  It is an ideal test in ‘post-accident’, for cause, and on duty situations.

The convenience and ease in collection of oral fluid under observed conditions, together with significant advances in analytical technology has advanced oral fluid testing for drugs of abuse as an alternative to urine testing.

Analysis of Hair provides a much longer window of detection, typically 1 to 3 months.  Hence the likelihood of a false negative test using hair is very much less than with a urine test.  Conversely, a negative hair test is a substantially stronger indicator of a non-drug user than a negative urine test. Hair analysis can indicate frequency of drug use.

Hair samples are ideal for the detection of drugs over a longer period, but does not detect drugs used in the  5-6 days before collection of the hair sample.

Moreover, if the result of the test is important to the employer, there are clear advantages to using a test that will give clear results of drug use over an extended period rather than a test that will not detect drug use if the candidate abstains for a few days before the test.

Time frame or window of detection

Analysis of hair provides a much longer window of detection, typically 1 to 3 months as drugs and other substances remain fixed and trapped in the hair indefinitely after they are incorporated in the hair after drug use.

A negative hair test is a substantially stronger indicator that someone does or does not use drugs than a negative urine test, as it shows drug use, or absence of drug use, over a longer period. It can also indicate frequency of drug use.

Hair test reveals 3-4 times more drug users then urinalysis.

Drug testing can provide a screening mechanism for new employees as well as a deterrent for existing members of staff.

Urine and saliva shows what drugs have been used for a relatively short period, in the hours before sample collection (24-72 hours depending on the drug). In contrast, hair provides information of use over a much more extended period of the order of weeks or months. Abstention from use for 3 days will often produce a negative test result in urine but will still be detected in hair.

Abstention from use for 3 days will often produce a negative urine or oral fluid test result.

For the purpose of testing for safety in the workplace for example vehicle drivers, tests utilised are often on-site tests using urine or saliva. These tests provide an on-site ‘screened’ result within minutes, indicating that the donor may have taken illegal drugs or consumed alcohol. These samples should be sent to a laboratory for confirmation of the result.

Typical characteristic




Window of detection(*)

1 day

2 – 4 days


Length of abstinence from drugs to produce a negative result(*)

24 hours

2 – 4 days


Invasive collection




Risk of sample adulteration




(*) It depends on the drug, dose and frequency of use.

Posted in Accreditation, Alcohol testing, Hair drug testing, Workplace Drug Testing Tagged with: , , , ,