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Is a prescription a defence if you test positive for THC while driving?

Only in Tasmania, as of November 2026. Elsewhere, driving with any THC is an offence even if your cannabis medicine was prescribed.

Facts checked 13 November 20263 min readHow we research

In most of Australia, no. Driving with any detectable THC is an offence in every state and territory, and as of November 2026 only Tasmania has a defence in force for THC that was taken as prescribed.12 Roadside tests look for THC, not CBD, but many CBD products contain some THC.

Where does a prescription make a difference?

Place Position for prescribed THC
Tasmania No offence if the drug “was obtained and administered in accordance with the Poisons Act 1971”2
New South Wales Registration scheme passed on 17 September 2026, not yet in force34
Victoria No defence. Since 1 March 2025 a court may choose not to cancel the licence5
Queensland None. Zero tolerance reaffirmed6
Western Australia None. Applies “regardless of whether the THC comes from prescribed legal medicinal cannabis”7
South Australia, ACT, Northern Territory None8910

Tasmania. Driving while impaired remains an offence there.2

New South Wales. Under the scheme as passed, a “registered medical cannabis user” commits no presence offence if THC is below 50 nanograms per millilitre in saliva (3.5 in blood) and no alcohol or other illicit drug is found. Learner, provisional and commercial drivers are excluded.3 The law starts on a date set by proclamation. We could not confirm that a start date has been set, so the existing zero-tolerance rule still applies.

Victoria. The driver is still guilty, the fine stands, and the patient has to go to court to ask the magistrate not to cancel the licence.11

Queensland. “It is an offence in Queensland for a person to drive with any amount of THC in their system, whether it was prescribed or taken illegally.”12 Higher penalties apply from 1 December 2026.13

What if my product is CBD-only?

New South Wales, Victoria and Queensland have said people taking CBD-only medicine can lawfully drive if not impaired.141512 But a lawful CBD-only product may contain up to 2% other cannabinoids, which can include a trace of THC.16 No government source we found gives a safe amount. See how much THC can a CBD product contain?

Is impaired driving treated separately?

Yes. Driving while impaired by any drug, including a prescribed one, is its own offence. CBD can cause sleepiness, especially with alcohol or sedating medicines. See CBD side effects.

Ask your prescriber whether your product is Schedule 4 (CBD-only) or Schedule 8, and how much THC each dose contains.

Read the full guide: CBD and driving in Australia.

Footnotes

  1. Section numbers are those of each state’s road transport Act. Government summaries of the offence and penalties include: NSW Government https://www.nsw.gov.au/driving-boating-and-transport/demerits-penalties-and-offences/offences/alcohol-and-drug-offences/drink-and-drug-driving-penalties ; Victoria Legal Aid https://www.legalaid.vic.gov.au/drug-driving ; Government of Western Australia https://www.wa.gov.au/organisation/road-safety-commission/drink-and-drug-driving ↩

  2. Tasmanian Legislation. Road Safety (Alcohol and Drugs) Act 1970, s 6A. https://www.legislation.tas.gov.au/view/whole/html/inforce/current/act-1970-077 ↩ ↩2 ↩3

  3. Parliament of New South Wales. Road Transport Legislation Amendment (Medical Cannabis and Driving Offences) Bill 2026, as passed by both Houses. https://files.parliament.nsw.gov.au/fileapi/ParlFiles/GetArtifact?serverRelativeUrl=%2Fbill%2Ffiles%2F18920%2FPassed+by+both+Houses.pdf ↩ ↩2

  4. The Canberra Times. State sets agenda on medicinal cannabis drivers, September 2026. https://www.canberratimes.com.au/story/9352659/state-sets-agenda-on-medicinal-cannabis-drivers/ ↩

  5. Parliament of Victoria. Roads and Road Safety Legislation Amendment Bill 2024, Legislative Council amendment schedule (inserting Road Safety Act 1986 s 50(1F)). https://legislation.vic.gov.au/sites/default/files/2024-11/LC-Amendment-schedule-Roads-and-Road-Safety-Legislation-Amendment-Bill-2024.pdf ↩

  6. Queensland Government. Queensland Drug Driving Review, updated 26 June 2026. https://www.qld.gov.au/transport/safety/road-safety/drink-driving/drugs/queensland-drug-driving-review ↩

  7. Government of Western Australia, HealthyWA. Cannabis (medicinal cannabis). https://www.healthywa.health.wa.gov.au/Articles/A_E/Cannabis ↩

  8. Government of South Australia. Drug driving, updated 9 November 2026. https://www.sa.gov.au/topics/driving-and-transport/offences/disqualification-and-suspension/types-of-disqualification/drug-driving ↩

  9. ACT Government, City Services. Drink and drug driving. https://www.cityservices.act.gov.au/roads-and-paths/road-safety/drink-and-drug-driving ↩

  10. Northern Territory Legislation. Traffic Regulations 1999, reg 55A and Schedule 1A (version as in force at 28 May 2026). https://legislation.nt.gov.au/en/Legislation/TRAFFIC-REGULATIONS-1999 ↩

  11. Victorian Department of Transport and Planning. Medicinal cannabis: 1 March amendment, March 2025. https://www.its.vic.edu.au/wp-content/uploads/2025/03/Medicinal_Cannabis_1_March_Amendment_March_2025_FINAL.pdf ↩

  12. Queensland Parliament. Answer to Question on Notice No. 1224, 2020. https://documents.parliament.qld.gov.au/tableoffice/questionsanswers/2020/1224-2020.pdf ↩ ↩2

  13. Queensland Legislation. Transport and Other Legislation Amendment Act 2026. https://www.legislation.qld.gov.au/view/whole/html/asmade/act-2026-023 ↩

  14. NSW Government, Centre for Medicinal Cannabis Research and Innovation. Driving (information for patients). Read from a copy captured on 29 March 2026. https://www.medicinalcannabis.nsw.gov.au/patients/driving ↩

  15. Victorian Government. Medicinal cannabis and driving: patient fact sheet. https://edge.sitecorecloud.io/stategovernc45d-cftw-production-c9ca/media/Project/TransportWebsite/Forms/medicinal-cannabis-and-driving-patient-factsheet.pdf ↩

  16. Australian Government. Therapeutic Goods (Poisons Standard, October 2026) Instrument 2026. https://www.legislation.gov.au/F2026L01327/asmade/2026-09-30/text/original/pdf ↩

This page is general information, not medical or legal advice. Laws and evidence change; we show the date we last checked the facts at the top of every page. Talk to your doctor or pharmacist before starting, stopping or changing any medicine.

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