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Can You Drive When Taking Medical Cannabis?!

Medical cannabis and driving is complicated. As with most aspects of cannabis , driving is not a one size fits all approach. As this recent research study points out, there is little consensus on the degree and duration of impairment typically seen with medical cannabis use.

Effect of Medical Cannabis on Driving

A recent systematic review concluded that: In general, cognitive performance declined mostly in a THC dose-dependent manner, with a steady decline of impairment in the hours following THC administration. Doses of THC were lower than those typically reported in recreational cannabis studies.

In all the studies, there was no difference between any of the THC groups and placebo on any neurocognitive measure after 4 h of recovery. Variability in the dose-dependent relationship raises the consideration that there are other important factors contributing to the duration of neurocognitive impairment besides the dose of THC ingested.

What this review suggests is that impairment duration from ingesting THC is greatly dependent on the individual person taking the medication. It also suggests that for medical cannabis users, any impairment disappears after 4 hours, indicating the medical cannabis users are taking lower doses of THC than recreational users.

Driving and CBD Medication

Generally, if you are prescribed cannabidiol (CBD) medication, you are able to legally drive as long as you are not impaired. CBD can potentially cause drowsiness, fatigue, and lower blood pressure. It is recommended that you discuss this usage and risk of impairment with your doctor in order to keep yourself and others safe when driving. If your day-to-day activities requires driving, you may want to consider the CBD medication over THC (although please first consult this with your doctor). Click here to learn more about CBD and how you can acquire it.

Driving and THC Medication

If you are prescribed medical cannabis that contains any amount of delta-9-tetrahydrocannabinol (THC), then it is illegal to drive. This is because THC is a psychoactive cannabinoid, affecting cognitive and motor skills that are necessary for safe driving. Such skills that are affected by THC include attention, judgement, memory, vision and coordination. THC can also be detected in the body for weeks after initial cannabis consumption. This unfortunately means users can face fines and loss of their licence despite being unaffected by the drug at that point in time.

Doctors are also responsible for assessing their patient’s fitness to drive. If you are advised not to drive and you continue, practitioners are legally required to inform your respective state’s road and maritime services for your and others’ safety on the road.

Medically Prescribed Cannabis

There are a vast number of medical cannabis products and types that can be prescribed by your doctor. These products can come in the form of oils, sprays, capsules and more. They can be THC dominant, CBD dominant, or contain a specific mix of THC and CBD. Therapeutic THC doses are typically in the range of 5–20 mg, while CBD doses tend to be higher (e.g., 50–1500 mg).

As compared to black market cannabis, you would never know how much THC there is in a product and the concentration can be wildly inconsistent from batch to batch. It is far safer and even potentially cheaper to use medically prescribed cannabis in Australia. You can read more about medical cannabis prescriptions here.

Cannabis & Crash Risk

Older research suggests that cannabis-positive tested drivers are 1.1 to 1.4 times more likely to be involved in a crash. They are also found to be more liable for a crash. However other recent studies indicate that no significant increases in crash risk occurs with THC use, especially when the concentration of THC is low in the blood.

In a recent survey of Australians who use medical cannabis, most respondents (72%) believed that their medical cannabis use does not impair their driving. A similar percentage (71%) reported that their medical cannabis use does not affect their ability to assess their fitness to drive. Just over one-third (35%) of respondents reported typically driving within three hours of cannabis use. These findings highlight a need for patient education regarding the risks associated with driving under the influence of cannabis. Be sure to discuss these risks with your doctor or GP when using medical cannabis.

Mobile Drug Testing

All Australian jurisdictions carry out random mobile drug testing (MDT), similar to random breath testing for alcohol. If roadside tests are positive, your oral fluid is then subject to further analysis in government laboratories. The three drugs that are usually tested for are THC, methamphetamine (crystal meth) and 3,4-methylenedioxymethamphetamine (MDMA), with cocaine also tested for in NSW. MDT only tests for the presence of drugs and not for impairment, and that driving with the presence of an illicit drug (i.e., ‘mere presence’) is a separate offence from driving under the influence.

THC enters your system when cannabis products are smoked, vaporised, or eaten through contamination of the oral cavity. THC cannot be transferred from blood into oral fluid, meaning that products like THC capsules or patches are unlikely to give rise to a positive roadside drug test. There are no current legal prohibitions related to driving in patients using CBD-only products. There is also no evidence that CBD can give rise to positive roadside drug tests in the absence of THC.

Legal medical cannabis is not a valid defence against prosecution under MDT laws, and patients face potentially severe penalties for driving with legal THC products in their system. This is a major barrier for patients contemplating or receiving medical cannabis treatment. In particular, patients who live in remote areas who depend on being able to drive for their employment and quality of life are most affected.

Click here to read more about the penalties and possible consequences of driving under the influence of THC.

The Detection Time

THC is typically detectable in your oral fluid for 4 to 6 hours after smoking or vaporising it. This however is highly variable across individuals and depends on factors such as frequency of THC use. In blood, THC is commonly detectable for up to seven days, and in extreme cases, for up to 30 days. In urine, THC may be detectable for up to 24 days, depending on the sensitivity of the test.


Any substance that interferes with the complex task of driving can be dangerous. THC in general can have a more pronounced impairment on driving and should be handled with caution. Although CBD-only medication appears to have no significant traffic safety risk, it is best to consult with your doctor first before deciding to drive while consuming CBD. For more information about medical cannabis and driving, feel free to read this research article that reviews the evidence regarding cannabis and driving impairment. If you would like to book in a consultation with one of our doctors click here.

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