Hair drug testing for Pre-Employment

Karolina Baker Alphabiolabs

By Karolina Baker, Health Testing Specialist at at AlphaBiolabs
Last reviewed: 02/01/2024

Employers have a duty of care to their employees, and must ensure that they meet the health and safety requirements laid out by The Safety, Health and Welfare at Work Act 2005.

Part of this requirement means employers must ensure that their employees are not working under the influence of drink or drugs. 

In situations where safety-critical decisions need to be made (e.g. pilots or people who operate heavy machinery), the influence of drink or drugs can have disastrous consequences.

Many companies have implemented drug & alcohol testing policies to ensure the health and safety both of their employees and of the working environment. 

A drug and alcohol test may come in the form of a pre-employment drug screen. 

In this article, we look at pre-employment drug testing and why it is important. We also discuss hair samples for pre-employment drug testing, as well as some other sample alternatives that can be used for a pre-employment drug screen.

What is pre-employment drug testing?

A pre-employment drug test is a urine, saliva or hair test that looks for drugs. It is usually conducted before someone starts a new job. The drug test could be performed as part of the application process, or after a job offer has been made. 

A pre-employment drug test often screens for multiple drugs. This means that the sample usually only has to be collected once to test for the presence of several drugs. 

The results from the pre-employment drug test may be qualitative or quantitative, depending on the type of test used. Qualitative tests can tell you whether a drug is present in a sample, whereas quantitative tests can tell you whether a drug is present and at what quantity.

What is hair drug testing and how does it work?

Hair drug testing is a method of assessing the presence and quantity of drugs in a hair sample. 

When a person takes drugs, the drugs are broken down into metabolites in the liver. These metabolites and a proportion of the parent drug are deposited into the hair, either through the bloodstream, sweat, or sebum. 

Whereas alcohol metabolites are deposited on to the surface of the hair shaft, drugs and their metabolites are incorporated into the core of the hair shaft. 

On average, our hair grows at a rate of 1 cm/month. As the drugs and their metabolites remain in your head hair, a month-by-month pattern of drug use can be determined, for up to 12 months.

You can also get an overview of historic drug use with hair samples, e.g. a three-month overview. Deciding which hair analysis to perform (overview or segmented) depends on what information you need to know from the drug test.

When a person’s hair sample is received into the laboratory, it is segmented based on the testing requirements. For example, a hair sample that requires a six month-by-month drug analysis will be cut into six segments that are each 1 cm in length. 

The hair goes through a series of processes to prepare the sample for analysis using liquid chromatography-tandem mass spectrometry (LC/MS/MS). LC/MS/MS is highly accurate at detecting even very small quantities of drugs in a variety of different samples. 

Hair drug testing doesn’t just apply to head hair. We can also determine the presence of drugs in facial, body or pubic hair. The upside to using head hair versus other types of hair is that head hair can be segmented to determine the presence of drugs on a month-by-month basis, whereas body hair can only provide an overview of up to 12 months, depending on the length and type of body hair provided.

What are the benefits of implementing drug testing in the workplace?

Many companies choose to adopt a pre-employment drug screen for new employees. Some are also implementing a continuous or randomised drug testing policy.

The main benefit of have a drug testing policy in the workplace is the improvement of safety. If a job requires someone to be in charge of machinery and/or make safety-critical decisions, implementing drug testing in the workplace can provide the assurance that employees are fit to do the task at hand. 

Workplace drug testing also saves the company time and money. It is often seen as a deterrent, meaning some potential employees are less likely to finish the application process if they use drugs regularly and know that they will be subject to a drug screen before or during the course of their employment.

This also means it is less likely that a company will have to deal with staff sickness, poor performance, or other issues that can occur as a result of taking drugs. 

Pre-employment and continuous drug testing can make the workforce as a whole feel safer, as everyone is more accountable for their actions.

What are the workplace drug testing laws in Ireland?

In Ireland, it is legal for employers to implement a drug testing policy for their employees. Companies should only implement a drug testing policy if there is justifiable reason to do so. 

The Safety, Health and Welfare at Work Act 2005 states that employers have a duty to protect the health and safety of their workplace and therefore their employees. This means they must ensure that their employees are not working under the influence of alcohol or drugs. 

A potential or current employee is therefore expected to give consent to have their sample taken and tested for the presence of drugs or alcohol. However, an employer cannot force an employee to provide a sample for testing, and testing must only be carried out if informed consent has been obtained. 

A potential or current employee has the right to refuse a drug test.  However, depending on company policy, this may mean that a potential employee is not offered a job, and a current employee could face disciplinary action.

The testing process must also not be a breach of the employee’s human rights, and their privacy and data must be protected.

What are the employee’s rights?

First and foremost, a drug test may only be carried out if the employee has consented to it. 

An employee has the right to refuse a drug test.  However, depending on the employee’s contract and the company’s policy, refusal to partake in a drug test may result in disciplinary action. In some circumstances, refusal to participate in a drug test can lead to dismissal. 

For pre-employment drug tests, a company has the right not to hire someone if they refuse to provide a sample, or if they fail a drug test. 

Employees have the right to privacy and data protection, and the employer should have procedures in place to ensure that these rights are protected. 

Employees have the right to know what the drug testing policy for their company is. Employers may only perform drug tests on their staff if there is a drug testing policy in place, and the employee has agreed to it. The drug testing policy is often outlined in the contract; when a new employee signs their contract, they are agreeing to the terms set out within that contract.

Can an employee refuse a drug test?

Employees can refuse to take a drug test, and an employer cannot force an employee to take a drug test. An employer cannot perform a drug test on an employee without their consent or knowledge.

Although employees have the right to refuse a drug test, doing so may result in disciplinary action. 

The disciplinary action taken against an employee depends on the stance the employer takes. Consequences for refusing to take a drug test or failing a drug test should be outlined in the employee’s contract and the company’s drug & alcohol policy. 

In some instances, failing or refusing to participate in a drug test can lead to dismissal. People who operate heavy machinery or vehicles and are therefore involved in safety-critical decision making could potentially lose their job if they refuse to take part in a drug test. 

Read our article Can You Refuse a Drug Test?  for more information.

Can you fire an employee who has failed a drug test?

In some circumstances, failing a drug test can lead to a dismissal. 

The severity of punishment for failing a drug test should be detailed in the company’s drug & alcohol policy. All employees must be aware of the company’s current drug & alcohol policy. 

If your company has a zero-tolerance policy to drugs, then failing a drugs test may be viewed as gross misconduct, which can therefore be grounds for dismissal. Dismissal may be immediate or following a period of suspension while an investigation takes place. 

As an employer, your drug & alcohol policy should cover how you will support any employees who have admitted to having problems with substance abuse prior to a drug test. 

Those who come forward about substance misuse before taking a drug test should be supported in a way that protects both the health of the individual and the safety of the working environment. 

What drugs can be tested for as part of a pre-employment drug screen?

It might surprise you to know just how many drugs can be tested for in a pre-employment drug screen. 

The drugs that are tested for as part of a pre-employment drug test might vary between the type of test used (e.g. urine, saliva or hair test) and the laboratory performing the testing.

At AlphaBiolabs, the main drugs we test for are:

  • Amphetamine
  • Benzodiazepines
  • Buprenophine
  • Cannabis
  • Cocaine (including Crack Cocaine)
  • Ecstasy (MDMA)
  • Ketamine
  • Mephedrone (M-Kat)
  • Methadone
  • Methamphetamine
  • Opiates (including Heroin)
  • Phencyclidine (PCP)
  • Tramadol
  • Zolpidem

 We can also test for:

  • GHB
  • LSD
  • Spice
  • Steroids
  • Other drugs upon request

These drugs can all be tested for using hair samples. 

The main benefit of using hair samples as part of a pre-employment drug screen is that you can look at drug use on a month-by-month basis or as an overview, e.g. over three or six months.

What alternative samples are there for pre-employment drug testing?

Aside from hair, there are several other sample types that can be used for pre-employment drug testing, all with their own advantages and disadvantages.

Oral fluid or saliva tests are relatively quick and easy to perform. They require the individual being tested to fully saturate an absorbent swab with saliva. If someone has not used any drugs recently (usually within 48 hours, although this can depend on the substance taken), they will receive an instant negative result. If someone receives a non-negative result, then the oral fluid will be sent to the laboratory to undergo further testing. This will tell you what substance was taken and how much is in the person’s system. 

Oral fluid drug tests are good for workplace pre-employment or randomised drug testing because the device is compact, quick and easy to use. A negative result usually means no further confirmatory testing is required, so you can be assured that your employees are fit to carry out the task at hand. 

However, the detection window when using oral fluid devices is narrow. This is because it can only detect the presence of drugs within a 48-hour window.  

Urine is another common sample for pre-employment drug testing. The urine is collected in a special sample collection pot that can detect a number of different drugs. A negative result usually means no further testing is required, but a non-negative result may require confirmatory testing in the laboratory. 

Urine drug tests have a slightly longer detection window than oral fluid – about 4 days, although this  depends on what drugs have been taken. However, some people may find taking a urine sample to be unpleasant and embarrassing. It can also be harder for some people to give a urine sample, for example if they suffer from paruresis (shy bladder syndrome). Paruresis is not a medical condition, but it can make it more difficult for someone to give a urine sample. 

We can also test for drug use using nail clipping samples. Nail samples can provide a much longer overview of drug use, because the drugs become trapped in the keratin fibres of the nails. Depending on the nail clipping samples submitted, you can get an overview of up to 12 months. 

However, you cannot obtain a historic segmented pattern of drug use as you can with hair. Nail samples are therefore a good alternative for people who cannot submit hair samples.

Where can I get a hair drug test for workplace?

At AlphaBiolabs, we offer a wide range of drug testing options, include hair testing, to suit your workplace testing needs

We have been providing accredited drug testing services for members of the public, the legal sector, and the workplace sector for over 20 years.

Our laboratory can analyse a variety of samples for the presence of drugs and their metabolites, including oral fluid (saliva), urine, hair, and nails.

If you are interested in implementing a hair strand drug test for pre-employment drug screening, or are a contractor/freelancer/consultant who needs a drug test before starting a new job, call our dedicated Workplace Team on 0140 29466 or email

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Karolina Baker AlphaBiolabs

Karolina Baker

Health Testing Specialist at AlphaBiolabs

Karolina joined AlphaBiolabs in 2021, and holds the role of Health Testing Specialist.

As well as overseeing a range of health tests, Karolina plays an active role in the research and development of the company’s latest health test offerings.

Before joining AlphaBiolabs, Karolina worked as an Associate Practitioner at Mid-Cheshire Hospitals NHS Foundation Trust, and as a research assistant at the Turner Laboratory, within the Faculty of Biology, Medicine and Health at The University of Manchester.

Karolina’s main scientific interests include clinical genomics and genetic diagnostics. Her qualifications include a BSc in Molecular Biology and an MSc in Genomic Medicine.

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