Note: Drug driving laws in Australia are subject to ongoing reform. Prescribers should direct patients to their state or territory’s legal aid authority or transport department for the most current jurisdiction-specific advice.

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Patients prescribed medicinal cannabis — particularly THC-containing formulations — must be clearly informed of the legal restrictions around driving. These laws vary by state and territory and are evolving. This article outlines the current landscape as of mid-2025 and highlights recent legislative changes relevant to clinical practice.

Should patients drive while taking medicinal cannabis?

Whether a patient can lawfully drive while taking medicinal cannabis depends on the formulation prescribed, the state or territory in which they drive, and whether they are impaired. In most Australian jurisdictions, the law tests for the presence of THC — not impairment — meaning patients may face legal consequences even when not functionally impaired.

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Regardless of jurisdiction, no patient should drive while experiencing impairment or adverse effects from any medication, including medicinal cannabis. Key symptoms to discuss with patients prior to driving include:

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• Dizziness
• Hypotension
• Drowsiness or sedation
• Cognitive slowing or reaction time impairment

Impairment versus presence: the legal distinction

A critical distinction for prescribers to communicate to patients is that Australian roadside drug testing detects THC presence in oral fluid — not functional impairment. THC can remain detectable in saliva well beyond the window of pharmacological effect, meaning patients may test positive and face legal consequences even when they are not impaired.

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A 2022 meta-regression analysis found that blood and oral fluid THC concentrations are relatively poor and inconsistent indicators of cannabis-induced driving impairment, contrasting with the stronger relationship between blood alcohol concentration and impairment.⁴ Higher blood THC concentrations were only weakly associated with increased impairment in occasional users, and no significant relationship was detected in regular users.⁴

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This evidence highlights a significant inequity in current drug driving legislation for medicinal cannabis patients, and is driving ongoing law reform across multiple states.

How does medicinal cannabis affect driving?

A landmark 2020 study led by the Lambert Initiative for Cannabinoid Therapeutics at the University of Sydney found that CBD does not impair driving, while moderate doses of THC produce mild driving impairment lasting up to four hours.²

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A subsequent 2022 randomised controlled trial found that 1500mg of CBD — the highest daily medicinal dose — had no impact on simulated driving or cognitive performance.³

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These findings support the safety of CBD-only products for driving (provided no adverse effects are present) and help characterise the duration of THC-related impairment. However, because Australian law in most jurisdictions applies a zero-tolerance policy to THC presence rather than impairment, the clinical evidence does not currently translate to legal protection for THC-prescribed patients in most states.

Is it legal for patients to drive while taking CBD?

CBD-only medicinal cannabis treatments that contain no THC are legal to have in a patient’s system while driving in all Australian states and territories. Patients should be advised to confirm the cannabinoid content of their prescribed product, as some CBD formulations do contain trace amounts of THC.

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Even where a product contains no THC, patients should be advised not to drive if they are experiencing any adverse effects such as drowsiness or dizziness. CBD has a narrow side-effect profile but can cause sedation in some patients.

Is it legal for patients to drive while taking THC?

In most Australian states and territories, it is not legal for patients to drive with any detectable amount of THC in their system, even with a valid prescription. However, the legal landscape is shifting, with two states having recently introduced or amended relevant legislation. The current position by jurisdiction is summarised below.

Tasmania

Tasmania has a driving defence available to medicinal cannabis patients, but it is more nuanced than commonly understood. Under the Road Safety (Alcohol and Drugs) Act 1970, a person does not commit a drug driving offence if the prescribed illicit drug was obtained and administered in accordance with the Tasmanian Poisons Act 1971.⁹

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Critically, a 2024 Tasmanian Magistrates Court decision confirmed that this defence applies only where the prescription was issued by a medical practitioner practising in Tasmania. An interstate prescription does not qualify for the defence.¹⁰ This is an important point for any patient who has been prescribed medicinal cannabis outside Tasmania and is driving in the state.

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The Tasmanian Department of Health recommends that patients do not drive whilst being treated with medicinal cannabis, and a separate offence of driving while incapable of proper vehicle control due to drug use remains in force regardless of prescription status.⁹

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In September 2025, changes to the Poisons Act 1971 were introduced to the Tasmanian Parliament which, if passed, would enable prescriptions issued interstate for Schedule 8 medicines including medicinal cannabis to be dispensed in Tasmania — which may have implications for the driving defence in due course.¹¹

Victoria

Victoria introduced a significant reform to its drug driving laws effective 1 March 2025. Under the Roads and Road Safety Legislation Amendment Act 2024, magistrates now have discretion not to cancel the licence of a medicinal cannabis patient who tests positive for THC while driving, provided the patient holds a valid prescription and was unimpaired at the time.¹²

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Importantly, testing positive for THC while driving remains an offence in Victoria and fines still apply. The reform removes automatic licence cancellation only — it does not decriminalise THC-positive driving. Patients must still attend court to seek the benefit of the discretion.¹³

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A review of the law’s impact on road safety and patient outcomes is required to be tabled in Parliament by 1 March 2028.¹²

New South Wales

As of mid-2025, NSW applies a zero-tolerance policy for THC presence while driving. A valid prescription cannot be used as a defence. In May 2025, the Road Transport Amendment (Medicinal Cannabis — Exemptions from Offences) Bill 2025 was introduced to the NSW Parliament, which if passed would create a statutory driving defence for unimpaired patients with a valid prescription. This Bill had not yet passed into law at the time of publication.¹⁴

All other states and territories

Queensland, South Australia, Western Australia, the ACT, and the Northern Territory all currently apply zero-tolerance THC presence laws, with no defence available for medicinal cannabis patients. A valid prescription does not protect against fines or licence loss in these jurisdictions.

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Western Australia strengthened its drug driving laws in February 2025, introducing an immediate 24-hour driving suspension and $600 fine for those who test positive or refuse a roadside drug test.¹⁵

Detection windows by test type

The amount of time THC remains detectable varies significantly between individuals depending on frequency of use, body composition, metabolism, and the sensitivity of the test used. Approximate detection windows by test type are as follows:

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• Saliva (roadside): approximately 12 hours in infrequent users; up to 30 hours or more in frequent users⁵
• Blood: detectable for up to 6 days in regular users⁶
• Urine: detectable for up to 30 days in regular users⁵
• Hair: detectable for up to 3 months⁷

These figures should be communicated to patients as indicative only, given the degree of individual variability. For patients who drive regularly, clinicians should consider whether a CBD-only formulation is more appropriate under current legislation.

How long after consuming THC is it safe to drive?

Because Australian jurisdictions (with the partial exceptions of Tasmania and now Victoria) test for THC presence rather than impairment, there is no definitive timeframe that can be given to patients regarding when it is safe to drive after consuming THC. Even after functional impairment has resolved, THC may remain detectable in oral fluid.

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Clinicians should advise patients that if they are prescribed a THC-containing formulation and need to drive regularly, they face a significant legal risk under current laws in most Australian jurisdictions, and that this risk persists well beyond the window of pharmacological effect.

Key factors influencing THC detection

Variables that influence how long THC remains detectable include:

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• Total amount of THC consumed
• Frequency of cannabis use
• Route of administration
• Patient body composition (adipose tissue percentage)
• Metabolic rate
• Exercise levels
• Sensitivity and type of drug test used

Law reform: Drive Change

Drive Change is an Australian law reform campaign advocating for medicinal cannabis patients to have the same driving rights as patients prescribed other Schedule 8 medications. The campaign proposes a uniform national defence for patients who hold a valid prescription, are not driving dangerously, and cannot be shown to be impaired. Prescribers may wish to be aware of this campaign when discussing the legislative landscape with patients. Further information is available at drivechangemc.org.au.

State-specific resources for patients

For jurisdiction-specific legal information, patients should be directed to their state or territory legal aid authority:

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• New South Wales: Legal Aid NSW
• Queensland: Legal Aid QLD
• Victoria: Legal Aid VIC / Fitzroy Legal Service
• South Australia: SA Legal Services Commission
• Western Australia: Legal Aid WA
• Tasmania: North West Community Legal Centre / Youth Law Australia
• ACT: ACT Government drug driving page
• Northern Territory: Legal Aid NT

Clinical Summary

Prescribers have a duty to clearly inform patients of the driving restrictions associated with their medicinal cannabis prescription, particularly where THC-containing formulations are involved. The legal landscape is evolving, with Victoria introducing judicial discretion over licence cancellation from March 2025, Tasmania maintaining a qualified driving defence for locally-prescribed patients, and NSW considering a formal statutory defence. In all other jurisdictions, a zero-tolerance THC presence policy applies and a valid prescription does not constitute a defence.

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Patients taking CBD-only formulations are generally safe to drive provided they are not experiencing adverse effects. For THC-prescribed patients, particularly those who drive for work or regularly, clinicians should carefully consider whether the legal risks of THC-containing treatment are appropriate for that patient’s circumstances, and consider CBD-only alternatives where clinically suitable.