The duty is managing impairment — testing is just one tool, with strings attached
Your real duty is to manage impairment as a workplace hazard — whether from alcohol, drugs, medication or fatigue. There's no specific law requiring drug and alcohol testing, and not every workplace needs it. If you do test, you need a clear written policy and provisions in the employment agreement, it must be reasonable and respect privacy, and a positive test shows presence, not impairment.
The hazard isn't “drugs” in the abstract — it's a worker being impaired while doing something that could hurt them or others.
The HSWA treats impairment as a risk to manage, and its definition of a hazard expressly includes behaviour affected by drugs, alcohol and fatigue. So the question to start with isn't “should we drug-test?” but “how do we make sure no one is doing safety-critical work while impaired?” — from any source, including prescription medication and tiredness. Testing is one possible tool for that, not the goal in itself.
There's no specific law that requires — or governs — workplace drug and alcohol testing, and not every workplace needs it.
Employment New Zealand is clear that not every employer needs to test as part of managing health and safety risks. Testing is most justified where work is safety-sensitive — operating machinery or vehicles, work where impairment could seriously harm the worker or others. Some sectors, such as aviation, rail and maritime, have their own regimes. For many workplaces, managing impairment well doesn't require testing at all.
If you do test, the type needs to match a legitimate reason.
| Type | When it's used |
|---|---|
| Pre-employment | As part of hiring, often for safety-sensitive roles. |
| Reasonable cause | Where there are reasonable grounds to believe a worker is impaired — appearance, behaviour or actions. |
| Post-incident | After an accident or near-miss, to understand whether impairment was a factor. |
| Random | Only justified for safety-sensitive roles, and must be genuinely random — not based on suspicion. |
Don't subject a whole team to “random” testing because you suspect one person — that isn't random, and is hard to defend.
Testing without a sound policy and agreement behind it is a legal risk, not a safety win.
To test, you need a clear written drug and alcohol policy and testing provisions in the employment agreement, so workers know in advance what applies and what the consequences are. The policy must be reasonable, balancing the genuine health and safety need against workers' privacy and rights, and be consistent with the recognised testing standards. A positive test shows substances are present above a cut-off — it doesn't prove someone was impaired at the time — so avoid overstating what a result means.
This area sits across health and safety, employment and privacy law, and getting it wrong can be costly. NZOHS isn't a law firm — for a testing policy or a specific situation, get legal or specialist advice before you act.
Dependency is a health issue, and a punitive-only approach often backfires.
Employers may be expected to treat alcohol and drug dependency as treatable conditions, so build support and the option to seek help into your approach alongside any consequences. A culture where someone can raise a problem — their own or a concern about a colleague — without fear does more for safety than testing alone.
Keep your policy and procedures in one consistent system. Book a demo and we'll show you how it works — free 30-day trial included.
No. There's no specific law requiring testing, and Employment New Zealand is clear that not every employer needs to test. Your duty is to manage impairment as a health and safety risk; testing is one tool, most justified for safety-sensitive work.
You can, but only with a clear written policy and testing provisions in the employment agreement, and the policy must be reasonable and respect privacy. Testing is normally used pre-employment, for reasonable cause, post-incident, or randomly for safety-sensitive roles. This is a complex legal area, so get advice first.
Not necessarily. A positive test shows that substances are present above a cut-off level — it does not prove the person was impaired at the time. Some substances stay detectable long after any effect has worn off, so avoid treating a positive result as proof of impairment.
Random testing is only justified for genuinely safety-sensitive roles and must be truly random, not based on suspicion. Subjecting a whole team to “random” testing because you suspect one person isn't random and would be hard to defend. Use reasonable-cause testing where you suspect a specific individual.
Impairment can come from fatigue and prescription medication as well as alcohol and illegal drugs, and the HSWA duty covers all of them. Manage impairment from every source, not just the ones a drug test detects — fatigue, in particular, is a major and testable-by-no-device risk.
