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With medical cannabis now legal in the UK, and able to help people with a broad range of health conditions (from ADHD and anxiety to chronic pain and insomnia), many patients want to know:
‘Can I take my prescription and drive?’
There is no easy answer. Because it’s yes and no, shaped by a whole host of factors. It’s also not just about having a prescription; it’s really about impairment and your ability to drive safely.
To help you understand and ensure you stay both safe and law-abiding, let’s delve into the legal considerations around driving with a medical cannabis prescription.
Effects of Cannabis on Mind and Body
First of all, a warning.
Though nearly half of cannabis users believe it’s safe to drive while under the influence, and there’s data that shows legalising cannabis does not lead to more accidents, this is not scientific proof.
In reality, cannabis - like all prescription drugs - can cause short-term changes in how the brain and body function. When consumed with a low tolerance or at higher doses, it has increased potential to impair your ability to drive safely.
However, medical cannabis patients who regularly consume cannabis-based medication and understand the effects of a particular form or strain on their mind and body can and do make informed decisions about their ability to drive safely after consumption.
But it is important to understand how it can impact your mind and body. When consumed, chemicals in the cannabis plant (cannabinoids) cling to receptors that make up the endocannabinoid system. This system has two main components – the
brain and nervous system – and controls everything from memory and mood to sleep and pain.
When certain cannabinoids bind to receptors, this may activate the part of the brain that dictates how we feel pain, for instance, and thus trigger pain relief.
Effects of Cannabis on Driving
Considering the above, it's clear that using medical cannabis in certain situations can affect your ability to safely operate a vehicle. The key factor here is impairment.
Your prescribed cannabis medication will include a warning, advising you not to drive or operate heavy machinery if you feel impaired such as being drowsy or sleepy.
Only you can assess your level of impairment and decide whether your medication is negatively impacting your reaction times, coordination or focus.
And as any driver will know, carelessness can cost lives. Driving sometimes requires split-second decision-making, so sitting behind the wheel when you’re not feeling 100% is never a good idea.
A perfectly legal example: driving when sleep-deprived has been shown to be more dangerous than driving drunk.
Even if you are a long-term medical cannabis user with a good understanding of how cannabis impacts your mind and body, it is crucial to exercise extra caution when prescribed new forms of cannabis or a new strain.
You should never drive after consuming new medication until you know exactly how it affects you.
Influencing factors
Unlike alcohol, where tests measure a single chemical reflecting impairment, cannabis users might be less aware of their driving abilities due to its complex nature. Cannabis can affect some people for a longer duration than they might realise.
Cannabis comprises over 500 different compounds, including tetrahydrocannabinol (THC) and cannabidiol (CBD), which can have varying effects on the body. A medical cannabis prescription high in THC, the main intoxicating compound, is more likely to influence your ability to drive compared to a CBD-dominant one, which is non-psychoactive.
The delivery system can play a key role too. While vapourising cannabis flower will take effect quickly and last for a few hours, edibles or oils that contain THC take effect much later and last much longer.
And that’s before we even consider personal factors such as dosage, tolerance, past use, height and weight.
No matter what, THC will show up in your blood within minutes of consuming cannabis, and can stay in your system for up to 90 days. This is especially relevant in the event of a drug test. However, as a medical cannabis patient, due to your regular consumption, THC will often always be present in your system.
But, as long as your medical cannabis is prescribed by a doctor and you are not driving while impaired by the medication, you will have a medical defence for having THC in your system while driving.
UK Laws On Cannabis and Driving
In one sense, the law is clear:
The legal limit for THC is two micrograms per litre of blood. Any more, and you’re at risk of serious punishment (see below).
At the same time, medical cannabis is legal, providing patients with a legal defence for having it in their system. Remember, if you are a medical cannabis patient, the key is not driving if you feel impaired and to only drive if it feels safe to do so.
Prescription Cannabis and Driving Laws
Anyone taking a medical cannabis prescription containing THC (even a small amount) will likely exceed the legal limit.
That said, it’s discriminatory to prosecute someone based on a medical condition, if they have a legitimate prescription. At this point, context is key.
If a medical cannabis patient can prove their driving was not impaired at the time of an accident, it’s possible to challenge a prosecution, and win.
For some patients, like those with chronic pain conditions, for example, severe neck or back pain, medical cannabis can be essential for safe driving. Proper pain management enables them to move freely and maintain awareness on the road.
Ensuring safe and effective use of cannabis for medical purposes can help these individuals lead more functional lives without compromising road safety.
However, regardless of the health benefits, patients should always consider whether their ability to drive safely is impaired before they sit behind the wheel.
Roadside Drug Tests for Cannabis
If the police suspect you are driving unsafely, or under the influence of a drug, they are within their rights to pull you over.
First off, they’ll likely conduct a ‘field impairment assessment’ (e.g. checking your pupils; asking you to walk in a straight line). These steps are vital, as tests are less about consumption, but whether or not you’re impaired.
From there, they may opt for a roadside drug test, which swabs the mouth for traces of cannabis and cocaine. If you fail, you’ll be arrested, taken to a police station and asked to complete a blood or urine test.
Penalties For Drug-Driving
If convicted without a medical defence, or impairment is determined regardless, the punishment for drug-driving can include:
- A driving ban (minimum 12 months)
- An unlimited fine
- Up to six months in prison
- A criminal record
A drug-driving conviction will also stay on your driving licence for 11 years. This can see car insurance costs rise steeply, cause problems in certain jobs, and could stop you travelling to certain countries (e.g. the US).
Summary
- Compounds in the cannabis plant bind to and activate receptors that could influence driving ability.
- Things like strain, form, tolerance, dosage and delivery system all dictate a person’s response to cannabis. THC stays in the body for a long time and may show up on a drug test long after use.
- If prosecuted, medical cannabis users with a valid prescription have some protection under UK law, but only if the person can prove their driving was not impaired.
- A drug-driving conviction comes with severe penalties, such as a driving ban, large fine, prison sentence and criminal record.
For more information about driving with medical cannabis:
1) Faculty of Pain Medicine Driving and Pain information for patients’ leaflet