Medical cannabis patients who need to drive are in a difficult spot. Australia’s driving laws prohibit anyone with any amount of tetrahydrocannabinol (THC) in their system from getting behind the wheel – even if they show no signs of impairment. This makes medical cannabis different from every other prescription medication.
It’s true that THC can impair driving and that no one should drive while impaired by any medication. However, the amount of time it takes THC to leave the body means that driving, even days or weeks after consuming medical cannabis, can put a patient at risk of producing a positive drug-screening result.
Until the laws are modified to better protect medical cannabis patients, you should avoid driving if you’re currently taking medical cannabis. However, it’s still important to understand the effects of THC, how that can impair driving and why it can take so long for THC to exit your system.
How Does Medical Cannabis Affect Driving?
THC is the compound in medical cannabis that causes a psychoactive effect (commonly known as a “high”). If your prescription contains THC, you will not legally be able to drive until your body has processed and excreted the THC from your system. However, this is tricky as THC is readily stored in fat tissue and can slowly re-enter the bloodstream days or weeks after consumption.
THC’s intoxicating effects can impair your ability to drive safely. A recent review looked at the research around cannabis and driving ability, and found that THC can affect the following areas that are important in relation to driving:
divided and sustained attention
how well you can track and follow objects or movement
fine motor coordination
fluid intelligence (how well you can adapt to new situations).
Being impaired in one or more of these areas can make it difficult to drive. The review also highlights that better measures for detecting impairment in cannabis users are needed, since current measures may not fully assess whether someone is actually impaired by THC.
A 2022 study found evidence that THC concentrations in blood or saliva may not be a wholly accurate way of measuring intoxication. The study’s authors aren’t suggesting that THC doesn’t cause impaired driving. However, they do state that more accurate methods to detect cannabis intoxication may be needed in Australia, especially for those who use medical cannabis regularly to help manage chronic conditions.
Can I Drive After Using Medical Cannabis In Australia?
It’s illegal to drive with any amount of THC in your system in all Australian states except Tasmania. In Tasmania, while it remains illegal to operate a vehicle with THC in your system, if you are a medical cannabis patient you can claim an exemption as long as your THC levels are minor and you are not currently impaired.
This means that you can’t drive after using any cannabis flower, oil, concentrate or any other THC-containing product.
Given that this makes medical cannabis different from other prescription medications and that there's the added uncertainty for patients of not knowing precisely when your system would be clear of THC, it's unsurprising that a growing chorus is calling for immediate change to these unfair laws.
Driving & CBD Oils
There is one exception: isolate CBD oils. These oils have been rigorously processed to remove all traces of THC and, as such, are the only medical cannabis products that you can be confident won’t produce a positive test.
If you do want to take CBD and drive, it’s important that you check your prescription and product information to ensure you have a true CBD isolate product. If you’re unsure, ask your doctor about your prescription and whether it’s safe or legal to drive while using it.
CBD is a non-psychoactive compound, meaning it is likely safe to use before driving. However, CBD can cause drowsiness, fatigue, nausea & low blood-pressure, so it’s important to be aware of how CBD affects you before you get behind the wheel.
How Long Should I Wait After Consuming Medical Cannabis Before Driving?
Unfortunately there’s no easy answer to this question. How our bodies process THC and other cannabis compounds isn’t as straightforward as other intoxicating substances such as alcohol. THC is lipid-soluble, meaning it can easily dissolve into lipids (fats) in your body, where it is then released into your blood stream over time.
As a result, the only safe option is to abstain from driving if you’re taking medical cannabis products that have THC in them.
How long THC stays in your system can vary greatly from person to person. It will depend on the amount of cannabis you’ve consumed, how you consumed it, how much body fat you have and how often you consume cannabis, along with other individual considerations such as genetics, metabolism, medication usage and certain medical conditions.
The most common random drug test you'll encounter while driving in Australia is a saliva test. If you use medical cannabis infrequently, saliva tests could detect THC in your system up to 12 hours after you consumed cannabis. If you are a frequent user, THC may show up on a saliva test up to 3 days after use. It should be noted that these times are estimates and will vary from person to person.
If you do test positive for THC, the positive sample will be sent to a laboratory for further analysis. The police may require additional testing to confirm the presence of THC, which might involve a blood or urine test.
If you’re involved in a road accident where you or someone else is injured, you will have to provide a blood sample to the police. If your blood contains THC, it may be used as evidence against you.
Playing It Safe With Medical Cannabis And Driving
In Australia there is a growing movement to make driving laws less prohibitive for medical cannabis users, while still maintaining safety on the roads. As the research develops and public opposition grows, we may see changes in legislation for medical cannabis patients – already 99% of medical cannabis patients believe there needs to be a change.
However, until driving laws are modified to better accommodate medical cannabis patients, you may need to seek alternative transport or switch to an isolate CBD product. These options obviously aren’t ideal for many people, so speak with your doctor if you’re wondering how you can best manage your health and still be able to legally drive.