A supervisor believes a worker may be impaired at the start of a shift. The worker is due to drive a forklift, use machinery or visit customers, and the manager wants a breath test or dismissal immediately. The first priority is to control the immediate risk. The next is to establish reliable facts without turning suspicion into a conclusion. A measured response protects people, preserves evidence and gives the employer a defensible basis for any health, conduct or capability decision.
Make the immediate work safe
Remove the person from safety-critical work while the concern is assessed. That can include driving, operating plant, electrical work, work at height, handling hazardous substances, clinical tasks or responsibility for other people. Use a calm, private instruction and explain that it is a temporary safety control, not a finding of misconduct.
Do not allow someone who may be impaired to drive home. Arrange a taxi, a lift from a suitable person or another safe journey. If urgent medical help appears necessary, use the appropriate emergency route. A colleague should not physically restrain, search or confront the person unless there is an immediate danger and the action is lawful and proportionate.
Secure keys or access cards where necessary, cover the task with a competent person and preserve relevant CCTV or work records. For a contractor or agency worker, control the site risk first and then involve their employer.
HSE: drugs and alcohol in the workplace ↗ · Related guide: workplace transport risk assessment →
Describe what was observed, not what you assume
Record observable facts as soon as possible: time, place, work due to be performed, speech, balance, alertness, behaviour, odour, mistakes and what the person said. Separate each witness's own account. Phrases such as ‘eyes appeared unfocused and they stumbled twice’ are more useful than ‘they were drunk’. Record normal explanations offered by the employee as well as facts that support the concern.
HSE warns that mood changes, absence, reduced performance and accidents can also indicate stress or illness. Prescription medicines, diabetes, neurological conditions, fatigue and mental distress can produce signs that resemble intoxication. Ask an open question about whether the person is well enough to work and whether they need medical help. Do not demand a diagnosis in front of colleagues.
Two managers can attend where practical, but avoid an intimidating interview. Detailed questioning should wait until the person can participate properly and has been told the allegation and process.
Related guide: practical manager checklist for employee health conditions →
Check the policy before considering a test
Drug or alcohol testing is not an automatic management right. GOV.UK says workers should consent, the policy should be in contracts or the handbook, testing should be limited to workers who need it and random testing should be genuinely random. Singling out an individual requires justification connected to their job or the facts.
HSE says testing is more likely to be justified in safety-critical work and should sit within a wider policy rather than operate as the policy itself. Check who may authorise a test, what substances or alcohol threshold are covered, the testing method, chain of custody, confirmation process, medication disclosure, result review and consequences of refusal. A quick screening result may require laboratory confirmation; it should not be treated as proof of current functional impairment without considering timing, method and other evidence.
Testing involves special-category health data. Document the purpose, lawful basis, special-category condition, necessity, access, retention and less intrusive alternatives. The ICO says high-risk monitoring may require a data protection impact assessment. Consent to the physical test does not remove those duties.
GOV.UK: drug testing at work ↗ · HSE: screening and testing ↗ · ICO: workers' health information ↗
Check the policy, evidence and data safeguards first.
HR + SAFETY can help North East SMEs set a proportionate response, review testing arrangements and protect the fairness of the later employment process.
Discuss an impairment concernKeep the health and conduct questions separate
Possible impairment can raise different issues. Reporting for work after drinking may be conduct. A prescribed medicine may require a temporary adjustment. Dependency may need medical support and a capability discussion. Possession, supply, unsafe conduct and refusal to follow a reasonable safety instruction may each require a different allegation. Do not collapse them into a single accusation of substance misuse.
HSE advises employers to encourage people with an alcohol or drug problem to seek help and to preserve confidentiality. Where dependence may be involved, consider occupational-health input, treatment support, temporary transfer from safety-critical duties and reasonable time for recovery. Support is not a promise to tolerate ongoing serious risk, but it should be considered before the employer decides that dismissal is the only response.
The Equality Act 2010 (Disability) Regulations 2010 exclude addiction to alcohol, nicotine or another substance from the disability definition, unless it originally resulted from medically prescribed drugs or treatment. An underlying or resulting physical or mental condition may still qualify in its own right, so obtain facts before deciding whether adjustments apply.
HSE: supporting an employee ↗ · Legislation: Equality Act 2010 (Disability) Regulations 2010 ↗ · Related service: occupational health →
Investigate before choosing the outcome
Once the person is fit to engage, set out the concern and gather evidence. That may include witness accounts, relevant records, the employee's explanation, policy wording and any properly obtained test result. Look for evidence that challenges the allegation as well as evidence that supports it. Keep medical details restricted to people who genuinely need them.
Suspension is not automatic. Consider temporary alternative duties, remote work, removal from a particular site or a restriction on driving or equipment. If paid suspension is necessary because the risk cannot otherwise be managed, keep it neutral, as brief as possible and under review.
Serious incapability caused by alcohol or illegal drugs can be treated as gross misconduct under a disciplinary policy, but the label does not decide the case. Acas requires an investigation, written allegation, reasonable preparation time, a hearing, the right to be accompanied where it applies, a reasoned decision and an appeal. Consider role, safety consequences, policy clarity, evidence, previous treatment of similar cases, mitigation and whether support is appropriate.
Acas: disciplinary procedure step by step ↗ · Related guide: workplace investigation process → · Related guide: suspending an employee →
Manager decision checklist
For a North East engineering firm, logistics operator, care provider or hospitality business, the first 20 minutes can shape both safety and the later HR decision. Give supervisors named contacts and authority to stop unsafe work. Rehearse the response before an incident occurs.
Law and official guidance were checked on 4 November 2026. The right response depends on the work, the evidence, the policy, the testing arrangements and the employee's health context. Where those facts are unclear, hold the immediate safety boundary and seek specific advice before making a final employment decision.
- Stop safety-critical work and explain the temporary control calmly.
- Move the conversation somewhere private and assess whether medical help is needed.
- Arrange safe transport; do not allow suspected impairment followed by driving home.
- Record specific observations, timings, witnesses and the employee's explanation.
- Preserve relevant records without collecting unrelated personal information.
- Check the contract, policy, role and grounds before requesting any test.
- Use a competent, reliable testing process with confirmation and chain-of-custody safeguards.
- Document the data-protection basis, necessity, access and retention for test information.
- Separate possible health, capability, conduct and criminal issues.
- Consider support, occupational health and temporary adjusted duties where appropriate.
- Use the least restrictive workable interim measure and review it.
- Investigate, hold a fair hearing, give written reasons and offer an appeal.
Treat suspected impairment as an immediate safety concern and an evidence question, not an instant finding of misconduct. Stop risky work, arrange safe transport, record observations, follow any testing safeguards, consider health support and use a fair process before deciding the outcome.
This guide provides general information for UK employers. It is not legal advice and should not replace advice based on the facts of a specific matter.