Medical conditions and reviews

Medicinal cannabis and driving resources for health professionals

Information and resources for health professionals to support conversations and advise patients about medicinal cannabis and driving.

Fitness to drive is an important consideration in the clinical care of patients. This includes considering the impact of the patient’s medical condition(s) as well as any potential impairment associated with treatment.

For medicinal cannabis there's an additional consideration as, under the current Victorian drug driving laws, it's an offence for a person:

  • to drive with any detectable amount of delta-9-tetrahydrocannabinol (∆9 THC*) in their system
  • to drive when impaired by any substance.

The Department of Transport and Planning (DTP) is actively encouraging drivers to discuss the implications of medicinal cannabis treatment on driving with their medical practitioner. This means health professionals are likely to be asked by a patient: “Can I drive while taking medicinal cannabis?” 

More information and answers to frequently asked questions about medicinal cannabis can be found at medicinal cannabis and driving.

* ∆9 THC is the main psychoactive component in cannabis but there are a number of other types that may be present. For the purposes of this fact sheet, the term THC is used when referring to ∆9 THC.

Resources to support your conversations with patients

Our medicinal cannabis and driving decision support resource (PDF) and driving needs checklist (PDF) can assist health professionals in addressing a patient’s driving risk when considering medicinal cannabis as a treatment option.

Our medicinal cannabis and driving fact sheet can be provided to patients to explain the current drug-driving laws and the impairing effects of medicinal cannabis.

Key considerations

  • Consider a patient’s driving needs before prescribing medicinal cannabis.
  • Educate your patient about medicinal cannabis and driving to ensure they are informed.
  • If a person is taking Cannabidiol (CBD)-only medicines, they can lawfully drive as long as they are not impaired.
  • Patients taking THC-containing products are at risk of driving while impaired and also testing positive at roadside saliva testing. They also risk testing positive for THC in blood testing if they're involved in a crash.
  • Due to the impairment risks, THC-containing products are usually not suitable for commercial vehicle drivers, and should be considered carefully for all drivers.
  • Impairment risk and road safety are affected by a number of factors, that should be taken into consideration and monitored when prescribing and dispensing medicinal cannabis.
  • Patients should be advised whether the underlying condition for which medicinal cannabis is being considered needs to be reported to Medical Review. 

Road safety laws and medicinal cannabis

What does the law say about medicinal cannabis and driving? 

There are two main types of cannabinoids that are likely to be found in medicinal cannabis, delta-9-tetrahydrocannabinol (Δ9 THC or THC) and cannabidiol (CBD). THC is the main psychoactive component.

It's an offence in Victoria for a person to drive with any detectable amount of THC in their system. This includes any detectable amount of THC from prescribed medicinal cannabis or recreational cannabis. Penalties for drug-driving include a mandatory driver licence suspension, monetary fines and completion of a mandatory behaviour change program.

It's also an offence in Victoria to drive a motor vehicle while impaired by any substance or prescription medication, including medicinal cannabis. Penalties for impaired driving can include licence cancellation and potential imprisonment. 

From 1 March 2025, magistrates will have the option to decide whether or not to cancel a driver’s licence of a person who tests positive for THC and is using prescribed medical cannabis.

For more information about the rules on medicinal cannabis and driving, visit medicinal cannabis and driving.

What does this mean when advising patients about driving?

  • If a person is taking CBD-only medicines, they can lawfully drive as long as they aren't impaired.
  • Regardless of impairment, driving with the presence of THC is an offence. The person can't drive legally if they have any detectable amount of THC in their system. Roadside testing involves testing of saliva. Note that the clearance rate of THC from the body is variable and THC can be detectable in saliva many hours after administration, depending on a range of factors. Thus, definitive advice can't be provided about timing of administration and driving. Drivers need to be aware that it's also a serious offence to refuse a roadside drug test.
  • If the person is involved in a crash that results in death or injury, they'll be required to provide a blood sample to Victoria Police for analysis. The presence of THC (including THC from medicinal cannabis) in blood can be used as evidence for prosecution purposes and may also affect vehicle and personal injury insurance claims.

More information about drug driving penalties.

In addition

  • A valid prescription for medicinal cannabis can't be used as a defence against a charge of testing positive for THC on a roadside drug test. From 1 March 2025, magistrates will have the option to decide whether or not to cancel a driver’s licence of a person who tests positive for THC and is using prescribed medical cannabis.
  • Drivers testing positive to THC at the roadside will be ordered by police not to drive for at least 12 hours.
  • Drivers are required to inform Medical Review if they have a long-term medical condition, disability, or injury that could affect their fitness to drive.

In relation to the laws about driving with the presence of THC, it's important you also understand that:

  • impairment generally increases as THC levels increase in the blood and saliva. However, current evidence suggests there's a weak or inconsistent correlation between levels of THC in blood and levels in saliva and the degree of impairment.
  • the level of THC measured in saliva doesn't reflect the level in blood.

Reporting to Medical Review

While drivers are responsible for their safety on the road and for complying with road safety laws, they rely on advice from healthcare practitioners about the impact of their medical conditions and treatments on their driving ability, including when they should report to Medical Review.

If a patient is advised not to drive and they continue to do so, practitioners can inform Medical Review anonymously. Find out more about making a report to Medical Review and what happens after you notify Medical Review.

For further information about the ethical and legal considerations for reporting, see Assessing Fitness to Drive.

Impairment and safe driving

Impairment risk depends on the type of cannabinoid 

An important consideration for safe driving is whether the medicinal cannabis product contains THC. However, even CBD preparations can cause drowsiness that can impair driving. 

Delta-9-tetrahydrocannabinol (THC)

This is the psychoactive component that causes the ‘high’ or euphoria sought by people who use cannabis recreationally.

It has been shown to impair the cognitive function and motor coordination needed for safe driving, particularly in the first few hours following consumption.

These effects can impair a driver’s ability to:

  • anticipate hazards and unexpected situations and respond accordingly
  • divide their attention to manage the driving task
  • make appropriate decisions and respond quickly to changes in the road environment.

These effects are not always evident until the person is in a complex situation that requires a rapid response, such as navigating an unfamiliar, busy traffic environment or avoiding an unexpected hazard on the road.

The impairing effects increase with increasing doses however, unlike alcohol, the blood levels do not correlate directly with the degree of impairment, and an accurate blood concentration range associated with impairment has not been determined.

These impairing effects are increased significantly when THC is combined with alcohol and some other medications.

Cannabidiol (CBD)

This substance isn't considered psychoactive and, therefore, doesn't have the impairing effects of THC.

It can, however, cause drowsiness, fatigue and lowered blood pressure, particularly at higher doses and when taken with other medications.

Impairment risk depends on several other factors

In addition to the type of cannabinoid, a range of other factors can contribute to the risk of impairment when driving, including:

  • the driving task including the effects of fatigue and shift work
  • comorbidities that may impair driving
  • individual genetics and metabolism
  • route of administration
  • dosage
  • naïve user effect
  • tolerance
  • drug interactions.

Advice for patients

It's important to have early discussions about driving with your patients so they can consider the potential impacts of medicinal cannabis on driving when making decisions about their treatment. 

Our medicinal cannabis and driving fact sheet provides information about road safety laws relating to drug driving and driving while impaired. 

Patients may be unaware of their road safety and reporting obligations. This includes whether their underlying condition (for which medicinal cannabis is being considered as a treatment) should be reported to Medical Review.

Most importantly, patients need to be aware that it's always an offence to drive while impaired by any substance or medication, including THC, and that it's an offence to drive with any detectable level of THC in their system.

More information

Note: It's acknowledged that this is a rapidly developing area and this information will be updated as reliable new evidence becomes available.

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