Medicinal cannabis prescriptions in Australia have grown at a pace few predicted. By the end of 2025, Therapeutic Goods Administration (TGA) data showed close to one million approvals, with prescribing rates climbing sharply since 2019. More than 800 different cannabis products are now available through the TGA's access pathways, and a growing share of those prescriptions are for inhaled, THC-dominant products with faster onset and stronger psychoactive effects.
For employers, this growth raises a practical and urgent question. A worker who holds a valid prescription is exercising a lawful right to medical treatment. But that prescription does not assess whether the worker can safely operate machinery, work at height or make split-second safety decisions while under the influence of THC. The employer's duty of care under work health and safety (WHS) law remains unchanged regardless of whether a substance is prescribed or not.
The challenge is not whether to act. It is how to act fairly, lawfully and effectively. Striking the right balance means understanding the legal framework, building disclosure processes that respect both privacy and safety, and choosing testing methods that reflect recent use rather than historical exposure.
Legal prescription does not mean workplace clearance
A prescription confirms that a medical professional has determined medicinal cannabis is an appropriate treatment for a patient's condition. It does not assess whether that patient can safely perform the specific duties of their role while taking the medication. These are two separate questions, and the employer is responsible for answering the second one.
Medicinal cannabis has been legal under federal law since 2016, accessed primarily through the TGA's Special Access Scheme or Authorised Prescriber pathways. However, most products prescribed in Australia are classified as unapproved therapeutic goods. This means the TGA has not formally assessed their safety, quality or efficacy in the way it would for a registered medicine. A University of Melbourne analysis published in March 2026 found that the regulatory systems designed to monitor benefit and harm have not kept pace with the volume of prescribing.
THC (tetrahydrocannabinol), the psychoactive compound in cannabis, can cause sedation, slowed reaction times, impaired concentration and reduced coordination. These effects are relevant to any role where alertness is critical, but they carry particular weight in safety-sensitive industries such as mining, energy, construction and transport.
The shift toward inhaled cannabis products is also significant. Inhaled THC is absorbed rapidly through the lungs, with effects felt within minutes. This creates a different risk profile from oral oils, which are absorbed more slowly and have a delayed onset. Employers managing impairment risk need to understand both the type of product prescribed and the timing of use relative to work hours.
The employer's duty of care under WHS law
Australian WHS legislation places a primary duty of care on employers (referred to in the legislation as persons conducting a business or undertaking, or PCBUs). Under the Model Work Health and Safety Act maintained by Safe Work Australia, this duty requires the employer to eliminate or minimise risks to health and safety, so far as is reasonably practicable. Impairment from any substance falls within the scope of this obligation, whether that substance is alcohol, an illicit drug or a lawfully prescribed medication.
The obligation does not change because the substance in question is prescribed by a health professional. A January 2025 WorkSafe WA information sheet made this point explicitly, stating that safety obligations take precedence regardless of prescription status. In Western Australia, the WHS Act 2020 and the WHS (Mines) Regulations 2022 govern workplace drug and alcohol obligations in the mining sector, with Regulation 641 setting out the specific requirements. Employers still referencing the superseded Mines Safety and Inspection Act 1994 should update their compliance frameworks accordingly, as that legislation was replaced from 31 March 2022.
Other states maintain comparable frameworks. Queensland's Coal Mining Safety and Health Act 1999 and New South Wales's WHS (Mines and Petroleum Sites) Act 2013 both address substance-related risks in high-hazard operations. South Australia's WHS Act 2012 and the Northern Territory's WHS (National Uniform Legislation) Act align with the national model. Across all jurisdictions, the principle is consistent: the employer must take reasonable steps to manage impairment risk, and a state-by-state breakdown of drug and alcohol testing obligations provides further detail on each regulatory framework.
Workers also carry obligations under WHS law. They must take reasonable care for their own health and safety and the health and safety of others who may be affected by their actions. They must also comply with any reasonable instruction given by the employer. This means a worker who is prescribed a medication that may cause impairment has a responsibility to cooperate with the employer's risk management processes.
Disclosure, privacy and reasonable adjustment
Employers need information about potential impairment to manage safety risk. Employees have a right to privacy over their medical information. Balancing these two obligations is one of the most sensitive aspects of managing medicinal cannabis in the workplace.
Medical information, including details of a medicinal cannabis prescription, is classified as sensitive health information under the Privacy Act 1988 (Cth). Employers cannot demand a worker's full medical history or contact a treating practitioner without the worker's written consent. However, employers can require workers in safety-critical roles to disclose any medication that may affect their ability to perform their duties safely. Most workplace drug and alcohol policies already include a clause to this effect, and the same principle applies to medicinal cannabis.
The way an employer handles disclosure matters. Policies should clearly explain what information will be collected, how it will be stored, who will have access and what the employer will do with it. Workers are far more likely to come forward if they trust the process is designed to support them rather than to penalise them. A non-punitive, consultative approach reduces the risk of workers concealing their medication use, which creates a far greater safety hazard than open disclosure.
Reasonable adjustment is also part of the picture. Under anti-discrimination law, employers must consider whether modified duties, adjusted rosters or alternative work arrangements could allow a worker prescribed medicinal cannabis to continue in employment safely. However, adjustments that compromise safety or fundamentally alter the inherent requirements of a role are not required. If a truck driver's role requires them to hold a licence and operate a vehicle, and their medication makes that impossible, an employer may be justified in concluding that reasonable adjustment is not available for that specific role.
One important boundary: employers cannot instruct a worker to change their medication. They can, however, work collaboratively with the worker and their treating practitioner to explore whether alternative treatments are available that would allow the worker to continue performing their duties safely.
Impairment risk assessment in practice
A risk assessment for a worker prescribed medicinal cannabis should follow the same principles as any other workplace hazard assessment, but it requires specific clinical input to be effective.
The assessment should consider four factors: the nature of the role (whether it involves safety-critical tasks such as operating machinery, working at height or driving), the specific product prescribed (including the THC content, the delivery method and the dosing schedule), the timing of use relative to work hours, and any advice from the treating practitioner or an independent occupational physician.
Impairment is not the same as detection. This distinction is critical. A positive drug test result for THC tells the employer that the substance is present in the worker's system. It does not confirm that the worker is currently impaired. THC metabolites can remain detectable in the body for days or even weeks after the psychoactive effects have worn off. Treating a positive test as automatic proof of impairment is both inaccurate and unfair, and it exposes the employer to potential claims under anti-discrimination and unfair dismissal legislation.
A layered approach to fitness-for-work assessment produces the most defensible outcomes. This means combining clinical assessment (an occupational physician reviewing the specific prescription, the role requirements and the individual's response to the medication), supervisory observation (trained managers recognising behavioural indicators of impairment such as drowsiness, slowed speech or coordination difficulties) and objective testing that reflects recent use rather than historical exposure.
Why oral fluid testing is the most relevant method
Oral fluid testing detects recent use of THC, typically within the preceding 12 to 24 hours. This detection window makes it a far better indicator of potential impairment than urine testing, which can return positive results for THC metabolites days or weeks after the last dose. For employers managing medicinal cannabis in the workplace, this distinction is significant. Australian Standard AS/NZS 4760:2019 governs the procedures for oral fluid drug testing and is the benchmark for compliance in Australian workplaces.
Urine testing, conducted under AS/NZS 4308:2008, remains appropriate for identifying historical or cumulative drug exposure. It has a well-established role in pre-employment screening and post-incident investigation. But in a context where the employer's primary concern is whether a worker is fit for duty right now, oral fluid testing provides a more relevant result. A worker taking medicinal cannabis in the evening for chronic pain management may test positive on a urine screen the following week, long after any impairing effects have passed. An oral fluid test administered at the start of a shift is more likely to reflect the worker's current state.
No workplace drug test directly measures impairment. This is an important limitation to acknowledge openly. Oral fluid testing is the closest available proxy for recent use and, by extension, the most probable window of impairment. It should form one component of a broader fitness-for-work framework that includes clinical assessment and supervisory observation.
For on-site screening at remote and fly-in fly-out (FIFO) worksites, the DrugSense DSO8 Plus V3 saliva drug test kit provides rapid oral fluid results verified against AS/NZS 4760:2019. Workplaces running higher-volume or more structured testing programs can use the DrugSense OraScan 3000 Analyser for instrument-based oral fluid analysis. Both options integrate with the Andalink cloud data management platform, which provides digital record-keeping, audit trails and compliance reporting across multiple sites.
Updating your drug and alcohol policy
Many existing drug and alcohol policies were written before medicinal cannabis became a mainstream prescription. Updating these policies is not optional. It is a practical step that protects both the employer and the workforce.
An effective policy update should address the following areas:
- Define impairment, not just detection, as the threshold for action. A positive test result alone should not trigger automatic disciplinary consequences without further assessment.
- Include a prescription medication disclosure clause that specifies the employer's expectations while providing clear privacy protections for the worker.
- Specify the testing method and the standard it complies with. For fitness-for-work assessments, oral fluid testing under AS/NZS 4760:2019 is the most appropriate method.
- Set out a clear escalation pathway: voluntary disclosure, risk assessment, occupational physician review, and adjusted duties where required and reasonably practicable.
- Build in regular review cycles. Prescribing trends, regulatory guidance and testing technology all continue to evolve, and a static policy will quickly fall behind.
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Incorporate supervisor training on impairment recognition, including how to approach a conversation with a worker about potential impairment in a way that is respectful and constructive.
Policy updates should be developed in consultation with workers and their representatives. This is both a WHS consultation obligation and a practical measure. Policies developed collaboratively are more likely to be understood, accepted and followed across the workforce.
Equip your workplace with the right testing tools
Oral fluid testing gives employers the most relevant indication of recent THC use. Andatech's DrugSense saliva drug test kits are verified against AS/NZS 4760:2019 and designed for on-site use in safety-sensitive environments.Browse Andatech’s saliva drug test kits or contact us for tailored workplace testing advice
