By EMA Health & Safety Advisor Rebekah Stephens
Implementing workplace drug testing in New Zealand isn’t as simple as buying a kit and lining up employees. It requires legal diligence, genuine consultation, and a commitment to doing it right.
The EMA’s employer AdviceLine frequently takes calls about drug and alcohol use and how to implement testing correctly. There’s no doubt it’s becoming more common. Data from The Drug Detection Agency (TDDA) shows workplace testing is ramping up and reflecting changing substance-use patterns. In March, TDDA added tramadol and fentanyl – two potent opioids – to their standard screening panel, and with good cause.
Employers have a duty to keep people safe and take reasonable steps to prevent harm, especially in safety-sensitive environments.
The starting point must be the reason for testing, which generally stems from obligations under the Health and Safety at Work Act 2015.
Because drug testing is a significant intrusion into privacy, it isn’t generally allowed unless clearly provided for in employment agreements or policies. Even then, it can only occur in limited circumstances outlined in the policy: pre-employment checks, random testing in safety-sensitive roles, or reasonable cause situations such as after an accident or when unusual behaviour is observed.
A well-drafted drug testing policy should explain why testing is being done, who it applies to, which substances are screened for, and which testing standards you’ll follow.
Consultation is critical. The Employment Relations Act requires good faith, meaning staff must be able to understand, ask questions, and provide feedback before the policy is implemented. Once finalised, employment agreements should link to it explicitly, making compliance a condition of employment.
Medicinal cannabis is an increasingly complex challenge for employers. While legally prescribed, it still may contain very low levels of THC, which can cause impairment and trigger a positive drug test.
Unlike alcohol, there is no agreed threshold for impairment, making it difficult for workplaces to balance safety obligations with respecting employees’ legitimate medical treatments.
Employees may believe they are protected by prescription use, but employers still carry legal duties to prevent impairment-related harm. The NZ Drug Foundation has highlighted the need for clearer guidance in this area, as businesses face growing uncertainty about how to manage medicinal cannabis fairly and lawfully. Employers are encouraged to update policies, consult openly with staff, and seek specialist advice before disciplinary action is considered.
Using an accredited testing provider ensures fairness. IANZ-accredited agencies follow strict chain-of-custody procedures and confirm non-negative results through accredited labs. DIY testing or unverified kits risk costly legal challenges.
The human element matters too. Managers should be trained to recognise impairment, document reasonable cause, and handle conversations with discretion. Policies must be reviewed regularly, with secure storage and timely destruction of results.
Workplace drug testing isn’t inherently difficult, but it demands a structured, transparent, and legally sound approach. Done properly, it protects people, reputation, and the ability to run a safe, productive business.