Driving and Medicinal Cannabis

In this context, we are referring to medicinal cannabis which is prescribed by a registered healthcare practitioner to relieve the symptoms of certain medical conditions. This information is not in relation to unregulated or non-prescribed cannabis products.

Currently the Royal Australasian College of Physicians advises that anyone taking medicinal cannabinoids should not drive.

Different cannabinoids affect the body differently. Therefore, different ratios of cannabinoids in medicinal cannabis products will have varying effects. 

Your suitability to drive depends on the type of treatment you have been prescribed, and this should be discussed with your doctor.

Research is underway in some Australian universities to determine if there is measurable level of cannabinoids in the blood at which driving capability is adversely affected. Until the results are released, the law cannot begin to be reviewed and changed.

There is no evidence that CBD affects driving. 

There are no legal driving restrictions for people taking prescription CBD only medicines.

However, like many other medications, CBD can cause drowsiness, fatigue and in some instances lowered blood pressure when first commencing the medication. These symptoms are seen more often when the CBD is taken at high doses or with another interacting medication so extreme caution is required when operating heavy machinery or driving.

In Australia, there is zero tolerance for driving with the presence of Tetrahydrocannabinol (THC) in oral fluid, blood or urine. Even if the driver has a prescription for medicinal cannabis, there is no exemption or legal defence for driving with even a trace of THC. 

THC can affect thinking and motor skills necessary for safe driving such as attention, judgement, memory, vision and coordination.

People taking medicinal cannabis need to be aware that THC can be detected in urine for many days after the last dose of medicinal cannabis. It can take up to five days for 80 – 90% to be excreted from the body. 

More research is needed in the area of driving and medicinal cannabis but so far the research has shown:

• vaporised cannabis containing THC can increase lane weaving and impair cognitive function in a driving simulator
• combining cannabis containing THC and alcohol dramatically impairs performance
• risks are greatest when a person first starts taking medicinal cannabis containing THC or if the dosage increases.

Unlike alcohol, a direct relationship between blood levels of THC and levels of driving impairment has not yet been established.

Read the Driving Factsheet from the Centre for Medical Cannabis Research