Medical cannabis and driving – your rights as a patient

Since medical cannabis was legalised in the UK in November 2018, an estimated 80,000 patients have gained legal access to cannabis-based medicines for the first time in almost 50 years. Despite this landmark move, and ever-growing patient numbers, there is still an astonishing lack of understanding about the laws and rights that apply to medical cannabis prescriptions.

One such topic that continues to produce stress and frustration for medical cannabis patients is the rules around driving. Patient forums and social media communities are awash with stories involving poorly educated police officers victimising them because of the medicine they are prescribed.

The good news is that as a patient, you can possess and take your medicine and continue to drive a motor vehicle, provided you meet certain conditions. Understanding the legislation relating to driving and medical cannabis use, and knowing your protected rights are key to resolving any unforeseen issues should you find yourself being told you are breaking the law.

Your rights as a medical cannabis patient who drives​

As a patient prescribed cannabis medicine, you have a statutory medical defence that allows you to drive with THC in your system above the specified limit (2 μg/L in blood), provided you meet these three essential conditions:

1. You are not impaired

1. The cannabis medicine has been prescribed to you, and you can provide evidence

1. You are following the directions provided by your specialist consultant and the instructions given by the manufacturer or distributor of the medicine

If you satisfy these conditions, you should not be arrested and have a complete defence to the offence of “drug driving” even if THC is detected in your system above the specified limit.

UK law regarding medical cannabis and driving​

UK law states that you are obliged to inform the Driver and Vehicle Licensing Agency (DVLA) of any condition that could potentially affect your driving. Prescribers are required to offer each patient guidance based on their specific circumstances, including their medical condition and the medicines prescribed to them.

NatCen’s government-sanctioned report on “Medical Cannabis and road safety” states: “In line with DVLA guidance, prescribers should give patients advice on driving while using medical cannabis, as they would with any other medication.” This includes being aware of possible interactions with other medications and monitoring patients’ responses to their medication – including those that could potentially impair driving.

It’s important to understand the distinction between the two sections of the Road Traffic Act:

• Section 4 focuses on impairment – this requires evidence that you were actually impaired while driving

• Section 5A focuses on threshold limits – this makes it an offence to drive with THC above 2 μg/L, regardless of impairment, unless you have a medical defence

As a legitimate medical cannabis patient, you have a statutory medical defence against Section 5A charges, but you must never drive while impaired, as this remains illegal under Section 4.

Your responsibilities as a medical cannabis patient​

As a medical cannabis patient who drives, you have several key responsibilities:

1. Never drive impaired​

• It is always an offence to drive while impaired by medicines or for any other reason

• You must honestly assess whether your driving might be impaired on any given occasion

• Do not drive if you experience sleepiness, poor coordination, impaired thinking, dizziness, or visual problems

• Take extra caution when first starting treatment or changing dosage

• Be aware that combining medical cannabis with alcohol or other medications can substantially increase impairment risk

2. Follow specialist and manufacturer guidance​

• Follow all directions provided by your specialist consultant

• Adhere to dosing instructions and guidance about use with other medicines

• Follow any accompanying instructions from the manufacturer or distributor

3. Carry evidence​

Wherever possible, carry the following documentation with you in your vehicle:

• A physical or digital copy of your most recent prescription

• Photo ID (e.g., driver’s license)

• If possible, a physical or digital letter from your specialist confirming you are their patient

• If carrying your medication, ensure it’s in its original packaging with your name on the label

Having this evidence readily available can help avoid unnecessary complications if you’re stopped by police.

What if I get stopped by the police?​

Regardless of impairment, which is thought to only last for around four hours or less, THC can remain in the blood, saliva, and hair for weeks after consumption. As a result, medical cannabis patients who are pulled over by the police and asked to take a roadside drug test may find themselves in a tricky situation.

Being convicted of drug driving in the UK can mean a minimum one-year driving ban, an unlimited fine, up to 6 months in prison and a criminal record.

If you are stopped by the police while driving as a medical cannabis patient, follow these steps:

1. Stay calm, polite, and compliant, you are not breaking the law

1. There’s no need to mention your medical cannabis prescription unless the police suspect cannabis use or impairment

1. If the police suspect cannabis in your system, calmly inform them that you are legally prescribed a cannabis medicine and have a medical defence

1. Share your documentation (prescription, ID, specialist letter) with them

1. Remind the officer that preliminary roadside tests only detect the presence of THC, not impairment, and that as a legal patient you have a statutory defence

1. If the police insist on a roadside swab, it may be best to comply while remaining calm

1. If asked to conduct a Field Impairment Test (FIT), comply, as refusal could result in a separate offence

What if I’m arrested despite having a medical cannabis prescription?​

If you are arrested and taken to a police station:

1. Request representation by either a solicitor of your choosing or the duty solicitor

1. Inform the solicitor of your medical defence and provide all evidence

1. If asked to provide a blood sample, comply with the request while maintaining that you have a statutory defence
2. Remain calm and cooperative throughout the process, remember you have a statutory legal defence if you were not impaired while driving

How is impairment determined?​

The law is clear: if you are not impaired while driving after taking medical cannabis, you have a statutory defence to protect you from prosecution. But how do the police determine your impairment? This is a question that contributes to significant confusion and debate, particularly as the vast majority of available data on the subject relates to the use of recreational cannabis.

This remains a grey area across all legal cannabis jurisdictions. The fact is, there is no reliable way to measure cannabis impairment. A roadside drug test will not test for impairment, it will only test for the presence of THC. However, THC can remain in your blood long after impairment has subsided, which can leave patients and the authorities alike in a difficult situation.

Currently, the police rely on Field Impairment Tests (FITs) to determine impairment. These tests measure markers such as balance and vital signs and include a pupillary examination. Only officers trained in FIT can conduct these tests, and they must record the test on body cameras. This evidence would be needed if a case goes to court.

Why are the police still unclear about medical cannabis and driving?​

Despite medical cannabis being legal in the UK since 2018 and there now being over 80,000 patients, there remains significant confusion among law enforcement regarding medical cannabis and driving laws. This confusion stems from several factors:

1. Lack of standardised training: Many police officers haven’t received adequate training on the 2018 changes to cannabis laws and patients’ statutory rights

1. Contradictory legislation: Cannabis remains on the “zero-tolerance” list under Section 5A of the Road Traffic Act despite being legal for medical use, creating an apparent contradiction

1. Testing limitations: Current roadside tests only detect the presence of THC, not impairment, leading to confusion about how to handle medical cannabis patients

1. Inconsistent guidance: There’s been limited official guidance for law enforcement on how to handle situations involving medical cannabis patients and driving

1. Communication gaps: Information about the statutory medical defence hasn’t been effectively communicated to all sections of law enforcement

The key takeaways​

As a medical cannabis patient who drives, remember:

1. You can drive with medical cannabis in your system provided you are not impaired and are following medical guidance

1. You have a statutory medical defence against exceeding the specified THC limit

1. Never drive impaired – this remains illegal regardless of your prescription

1. Always carry evidence of your prescription while driving

1. If stopped by police, remain calm, explain your situation, and present your evidence

1. If arrested despite having a prescription, request legal representation immediately

There is clearly still a long way to go to eradicate the stigma against medical cannabis and the patients that use it; however, medical cannabis patients can take a little comfort in the fact that several precedents now exist where cases against medical cannabis patients have been dropped or defendants found not guilty when proper evidence of prescription and compliance with medical guidance was presented. The statutory defence is robust when properly applied.

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