Article 8 - CBPM Patients and Driving: What the Law Says and What It Doesn't
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Being a CBPM patient does not disqualify you from driving. It does place responsibilities on you that most patients are not told about at the point of prescription. This article sets out what the law says, where it is silent, and what that means in practice.
For the practical steps you should take as a patient, see Article 9 - The Informed Patient.
The legal framework
Drug driving in the UK is governed by Section 5A of the Road Traffic Act 1988. It creates two separate offences. The first is driving with a specified controlled drug above a specified limit in blood. The second is driving whilst impaired by a drug, including a medicine.
THC is a specified drug under Section 5A. The legal limit is 2 micrograms per litre of blood. That limit was set at a level intended to capture recreational use, not therapeutic use. For some CBPM patients, particularly those on higher doses or those who medicate regularly, blood THC levels may exceed that threshold even when the patient is not impaired.
What the law does not provide
There is no statutory medical defence for CBPM patients under Section 5A for the per se limit offence. The medical defence that exists under Section 5A applies only in specific circumstances and has significant limitations in practice. It does not provide automatic protection for a patient who tests above the limit.
The law does not define impairment by reference to a blood level for cannabis. Impairment is assessed by a drug recognition expert and, ultimately, by a court. A patient who is below the per se limit can still be charged with driving whilst impaired if their driving or behaviour suggests impairment.
The APPG on Medical Cannabis under Prescription has raised the inadequacy of the current framework for CBPM patients. Reform is being discussed. It has not yet happened.
What CanCard does and does not do
CanCard is a scheme that allows CBPM patients to carry evidence of their prescription status. It is intended to inform police officers at the roadside that the individual is a prescribed patient, not a recreational user.
CanCard does not provide a legal defence. It is not a statutory document. A police officer is not legally required to treat CanCard as proof of anything. Its value is practical. It may prompt a different conversation at the roadside. It does not change the legal position if a blood test returns a result above the legal limit.
Patients should carry CanCard and their prescription documentation. Neither provides immunity. Both provide context.
The roadside testing gap
Roadside drug testing uses saliva swabs calibrated for recreational cannabis use. They are not calibrated for therapeutic use. A patient who has medicated within the preceding hours is likely to return a positive roadside swab regardless of whether they are impaired or whether their blood level is above the legal limit.
A positive roadside swab triggers arrest and a blood test. The blood test result determines the legal position. The roadside swab result is not itself evidence of an offence.
The consequences beyond a criminal charge
A drug driving conviction carries a mandatory minimum 12-month driving ban, an unlimited fine, a criminal record, and up to six months imprisonment. For many CBPM patients, loss of licence is not an inconvenience. It is a life-altering consequence that affects employment, independence, and access to medical appointments.
Insurance is a separate issue that patients rarely consider. Motor insurers are not required to cover a driver who commits a criminal offence. A CBPM patient involved in an accident while above the legal blood limit may find their insurer voids the policy. That applies regardless of whether the patient was impaired, regardless of fault, and regardless of whether they were prosecuted. The civil exposure from an uninsured accident adds to an already serious legal position.
Patients should check their motor insurance policy terms and, where necessary, disclose their CBPM status to their insurer. Failure to disclose a material fact can itself void a policy.
What patients need to understand
The law as it stands places CBPM patients in a position that has not been resolved by Parliament or by the courts. Patients who drive whilst prescribed cannabis-based medicines should understand the following.
THC has a longer detection window than its impairing effects. A patient who medicated the previous evening may not be impaired the following morning but may still return a blood result above the legal threshold. The gap between impairment and detectability is not reflected in the current legal framework.
There is no safe interval that applies to all patients. Metabolism varies. Dose, frequency, strain, and individual physiology all affect how long THC remains above the legal blood threshold. Patients should discuss this with their prescriber.
The absence of impairment is not a defence to the per se limit offence. A patient who drives carefully, who carries their prescription, and who is not impaired may still commit a criminal offence if their blood THC is above 2 micrograms per litre.
The lived experience
This is not an abstract legal problem. CBPM patients are being stopped, tested, arrested, and in some cases prosecuted under a framework that was not designed for therapeutic use. The roadside is not the place to discover how the law applies to you.
Know your position before you drive. Discuss it with your prescriber. Check your insurance. Carry your documentation. Understand that CanCard helps but does not protect you. And understand that the law in this area is likely to change, but has not changed yet.
This article is written for information purposes only. It does not constitute legal advice. If you have been stopped, arrested, or charged in connection with drug driving as a CBPM patient, seek legal advice from a solicitor with experience in this area.
If you have experience relevant to CBPM patients and the drug driving framework, clinical, legal, or lived, we want to hear from you.
glenn@puruslumina.com