Drug Testing in the Workplace: An Employer’s Guide

Workplace drug testing is a complex topic to navigate for businesses. On the one hand, employers have a duty to keep everyone safe. On the other, employees have the right to privacy and fairness. Striking the right balance comes from understanding the legal framework, and setting up clear policies that reflect both compliance and compassion.

This guide walks you through the legal landscape of workplace drug testing in the UK, the practicalities of when and how it can be carried out and what to do if an employee tests positive.

What is drug testing in the workplace?

Workplace drug testing is the process of checking whether employees or job applicants have drugs or controlled substances in their system. For employers, it is about creating a safe working environment, managing legal responsibilities and maintaining trust in the culture of the organisation.

It is particularly relevant in safety-critical roles where impairment could lead to serious consequences. But even in lower-risk environments, employers may still consider testing as part of a wider health and safety or wellbeing strategy.

Is workplace drug testing legal in the UK?

Yes, but there’s quite a bit of legal groundwork to cover first. Employers can’t simply decide to carry out drug tests without consent or justification. The main legal considerations are:

• Consent and contracts: Under UK law, employees must give consent for drug testing. This is usually achieved through contractual terms or workplace policies that employees have signed or acknowledged.
• Health and Safety at Work Act 1974: Employers have a duty of care to ensure the health, safety, and welfare of their staff. If an employee’s impairment from drugs creates a risk, an employer may have grounds to act.
• ACAS guidance: ACAS advises that drug testing should be carried out fairly, with clear policies in place, and only where it is justified. Employers should avoid singling out individuals without good reason.
• HSE perspective: The Health and Safety Executive encourages employers to manage risks effectively. In some industries, like transport and construction, drug testing is more common because the stakes are higher.
• Data protection: Results from drug tests are considered sensitive personal data under UK GDPR. Employers must process and store this information lawfully, securely and only for as long as necessary.

In practice, drug testing is lawful if it is proportionate, necessary for safety or compliance and handled transparently. Employers must always be able to show that testing is reasonable.

Legal consequences for employers

Getting drug testing wrong can have serious repercussions. Employers who fail to follow proper procedures may face employment tribunal claims for unfair dismissal, discrimination or breach of data protection. 

Compensation awards can be significant, especially where an employee’s reputation has been damaged. The Information Commissioner’s Office can also impose fines for GDPR breaches, and in safety-critical industries, HSE enforcement action could follow if inadequate drug policies contribute to incidents.

When and why might an employer test for drugs?

Drug testing should only take place where there is a clear reason, backed by policy. Here are the main scenarios where testing typically happens:

Situation	Legal Requirement	Justification Needed	Notice Required
Pre-employment	Contract terms	Safety-critical roles	Job advert/offer stage
Random testing	Contract + safety grounds	High-risk environment	Policy notification
Reasonable suspicion	Policy basis	Observable evidence	Immediate
Post-incident	Safety investigation	Accident investigation	Part of procedure
Return to work	Agreed support plan	Rehabilitation program	Mutual agreement

Pre-employment testing

Some employers choose to carry out drug tests before confirming a job offer, particularly in industries where safety is important. This ensures new hires are fit for work from day one.

Random testing

Random drug testing is lawful but only where there is a contractual basis and a clear health and safety justification. Employers must apply it consistently to avoid claims of unfair treatment. It is most commonly used in industries like aviation, transport and construction.

For-cause or suspicion-based testing

Employers may decide to test an employee if there are reasonable grounds to believe they may be under the influence of drugs. Signs could include erratic behaviour, reduced performance or evidence from an incident. Policies should set out what counts as reasonable suspicion.

Post-incident or return-to-work testing

Testing may be appropriate after a workplace accident or near miss, to check whether impairment played a role. Employees returning after rehabilitation may also be subject to agreed testing as part of their support plan.

Industry-specific requirements

Different industries face varying levels of risk and regulatory requirements when it comes to drug testing:

Industry	Risk Level	Testing Frequency	Typical Methods	Regulatory Context
Aviation	Very High	Regular + random	Urine/saliva	CAA requirements
Maritime	Very High	Pre-employment + cause	Urine	MCA regulations
Rail transport	Very High	Regular + random	Urine/saliva	ORR standards
Road transport	High	Pre-employment + cause	Urine/saliva	DVSA guidelines
Construction	High	Pre-employment + cause	Urine	CDM regulations
Oil & gas	Very High	Regular + random	Urine	OPITO standards
Healthcare	Medium	Pre-employment + cause	Urine	Professional body requirements
Office-based	Low	Pre-employment only	Urine	General H&S duties

In highly regulated sectors like aviation and maritime, drug testing may be mandated by law or industry standards. The Civil Aviation Authority, Maritime and Coastguard Agency and the Office of Rail and Road all have specific requirements that go beyond general employment law. If you’re in one of these sectors, it’s worth checking the specific regulatory guidance to make sure you’re covering all bases. If you’re unsure about what compliance your business falls under, our friendly HR Advisory team can help.

Workplace drug screening methods

There are a number of different screening methods for drugs in the workplace with varying accuracy, reliability and cost. Businesses should determine what works best for their industry and work environment. 

Common types of tests

The most common methods of workplace drug testing include:

• Urine tests: Inexpensive, widely used, and effective for detecting a broad range of substances, though not always good at measuring immediate impairment.
• Saliva tests: Easier to administer and useful for recent use, but they offer a shorter detection window.
• Hair tests: Capable of showing long-term drug use, sometimes up to 90 days, but less effective for detecting recent use and more expensive.
• Blood tests: Highly accurate but invasive and rarely practical outside medical settings.

Method	Detection Window	Accuracy	Cost	Invasiveness	Best Use	Limitations
Urine	1-3 days	High	Low	Medium	General screening	Privacy concerns, adulteration risk
Saliva	12-24 hours	Medium	Low	Low	Recent use/post-incident	Short detection window
Hair	Up to 90 days	High	High	Low	Long-term patterns	Poor for recent use, slower results
Blood	12-24 hours	Very high	High	High	Medical/legal accuracy	Invasive, requires medical supervision

Accuracy, reliability and timeframes

Accuracy can vary depending on the type of test. Urine and saliva tests are quicker but can be prone to false positives. Hair tests are better for spotting longer-term patterns but are less useful in post-incident scenarios. That’s why it’s best to get any positive result verified by a lab. To rule out false positives or anything that might mitigate the result. Employers should also factor in the time it takes to receive results, as delays can impact operational decisions.

Cost considerations

Drug testing costs vary a lot depending on the method chosen and the volume of tests needed. Urine tests can range from £15-30 per test, saliva tests £20-35, hair tests £80-150 and blood tests £100-200. 

Don’t forget to factor in both the initial test costs and follow-up lab confirmation, it can quickly add up. For smaller businesses, partnering with occupational health providers can make testing more cost-effective through shared services and bulk pricing.

Special considerations

Navigating drug testing in the workplace also needs to factor in how you handle prescription medications, contractors and international employees and travel. Ensure you’ve considered these elements when building your plan. 

Prescription medications and controlled substances

Employees taking prescribed controlled substances present a particular challenge. Common medications like opioid painkillers, ADHD treatments or anxiety medications may trigger positive results. 

Employers should have a clear process for handling these situations, typically involving a medical review officer who can assess whether prescribed medication affects safety performance. The key is distinguishing between legitimate medical use and substance misuse while respecting employee privacy.

Third-party workers and contractors

Many workplaces rely on contractors, agency workers and regular visitors who may need access to safety-critical areas. Employers should consider whether their drug testing policies extend to these groups and ensure contracts reflect any testing requirements. 

The responsibility for testing may lie with the contracting agency, but site controllers should verify that appropriate checks have been conducted.

International employees and travel

Employees who travel internationally or work across different jurisdictions may be subject to varying drug testing requirements. 

Some countries have zero-tolerance policies that are stricter than UK standards, while others may have different substances that are controlled. Employers should brief traveling employees on overseas requirements and consider how international assignments affect their drug testing obligations.

Policies and procedures for implementing drug testing

Building policies and procedures around workplace drug testing will require careful consideration from employers and, in most cases, require consulting with employment law specialists. 

Creating a clear substance misuse policy

A compliant policy is essential. It should outline when and why testing will take place, the methods used and what steps follow a positive result. It should also make clear that the aim is to keep employees safe and provide support where needed. This could feed into various areas of your policy, including leave management, disciplinary procedures, mental health support and even your onboarding process, so new starters understand expectations from day one.

If you need help creating a policy for your business, get in touch with our HR Advisory team. They can guide you through best practice, help ensure your documentation is aligned with current compliance regulations, and support you in setting the right tone for a safe and positive workplace.

Communicating testing policies to staff

Policies should be shared during onboarding and revisited regularly. Employers should avoid springing new rules on employees without consultation, which can cause stress and uncertainty. The more transparent you are, the more likely employees are to accept the policy as fair.

Ensuring consent and fairness

Testing without consent is always unlawful. You’ll need employee agreement, and whatever rules you set need to apply fairly across the board. Confidentiality is just as important. Mishandling results could expose employers to claims and reputational damage. It can also cause distrust between employees and employers, leading to poor morale.

Employees should also be clearly informed about which substances are being tested for, and the reasons why testing is being carried out. Testing should be limited to those substances relevant to the stated purpose and only to the extent necessary to meet that purpose. This ensures the process is proportionate and transparent.

Handling positive drug test results

Investigatory process and retesting

Employers should not rush into disciplinary action. A positive test should always be verified by laboratory confirmation. An investigatory process should follow, giving the employee an opportunity to respond.

Employee rights and appeal

Employees have the right to challenge the results and appeal any decisions. Employers should ensure the appeals process is fair, transparent and well-documented.

Disciplinary vs supportive response

The response to a positive test will depend on the situation. In some cases, disciplinary action may be appropriate. In others, offering support through an Employee Assistance Programme or rehabilitation could be a better solution. Employers should always act in line with their policy and maintain a balance between compliance and compassion.

Control measures for substance abuse at work

Drug testing should sit alongside wider measures that address substance misuse. Employers can reduce risks by offering training, creating awareness campaigns, and providing access to confidential support services. Carrying out risk assessments and embedding wellbeing strategies into the culture can also help prevent issues before they arise.

Substance abuse training for employees and managers

Training is not just about compliance. It gives employees the knowledge to understand the risks of substance misuse and where to seek help. For managers, it provides the tools to spot warning signs, handle sensitive conversations and escalate concerns appropriately. With the right training in place, potential problems can often be managed early.

How can Employment Hero help?

Navigating workplace drug testing is a complex topic for businesses of all sizes, but small-to-medium enterprises often feel more pressure. Between keeping up with legislation, protecting employee rights and building policies that feel fair, it can be a lot for employers to manage on their own. If you’re feeling unsure where to start, our team of employment law and HR specialists can help.

Through our HR advisory lines, you can speak directly with experts who understand the nuances of UK employment law and can guide you through sensitive situations. Our HR software also makes it easier to embed clear policies, share them with staff during onboarding and keep records consistent and compliant.

Reach out for tailored advice and support.

The information in this article is current as at 1 October 2025, and has been prepared by Employment Hero UK Ltd and its related bodies corporate (Employment Hero). The views expressed in this article are general information only, are provided in good faith to assist employers and their employees, and should not be relied on as professional advice. Some information is based on data supplied by third parties. While such data is believed to be accurate, it has not been independently verified and no warranties are given that it is complete, accurate, up to date or fit for the purpose for which it is required. Employment Hero does not accept responsibility for any inaccuracy in such data and is not liable for any loss or damages arising directly or indirectly as a result of reliance on, use of or inability to use any information provided in this article. You should undertake your own research and seek professional advice before making any decisions or relying on the information in this article.