# Driving on a medical cannabis prescription

Source: https://medcannaindex.com/guides/driving-on-a-prescription

You may drive on a medical cannabis prescription only if the medicine has not made you unfit to drive. THC has a very low legal blood limit of 2 micrograms per litre; a prescription gives a legal defence to being over that limit if you took the medicine as directed, but it is never a defence to driving while unfit. If you feel affected, do not drive. This is the law in England, Scotland and Wales.

What the law says about driving when you take prescribed medical cannabis, and how to stay inside it.

The short version

- It is illegal to drive if a drug, prescribed or not, has made you unfit to drive.

- There is a second offence of driving with more than a set amount of certain drugs in your blood. THC, the main active part of cannabis, is one of them, and its limit is very low.

- A prescription can give you a legal defence to the second offence, if you took the medicine as you were told. It gives no defence to driving while unfit.

The two offences

Driving while unfit. The government's guidance says: "It's illegal in England, Scotland and Wales to drive with legal drugs in your body if it impairs your driving." This applies whatever the drug is and however you came by it.

Driving over the limit. Section 5A of the Road Traffic Act 1988 makes it an offence to drive with more than a specified amount of certain controlled drugs in your blood. The limit for THC is 2 micrograms per litre of blood, which the government describes as a "zero tolerance approach". A patient taking a prescribed product that contains THC should assume they may be over it.

The medical defence

Section 5A gives a defence to the over-the-limit offence. You have to show all of these:

- the drug was prescribed or supplied to you for medical purposes;

- you took it as your prescriber directed, and as any instructions that came with it said;

- you held it lawfully.

The defence is lost if you went against advice about how long to wait between taking the medicine and driving. That advice can come from your prescriber or from the instructions with the medicine.

The defence does not cover driving while unfit. The government's guidance puts the two together: you can drive after taking a prescribed drug if you followed the advice on how to take it and it is "not causing you to be unfit to drive even if you're above the specified limits".

What this means in practice

- Do not drive if you feel affected. If you are drowsy, slower to react, or not sure, do not drive. The guidance says to talk to your doctor, pharmacist or healthcare professional if you are unsure whether you should drive.

- Ask your prescriber how long to wait. Ask them directly how long you should leave between a dose and driving, and ask for the answer in writing. The defence depends on following that advice.

- Carry proof. The government's advice is: "If you drive and take prescription medicine, it may be helpful to keep evidence of this with you in case you're stopped by the police." A copy of your prescription, the medicine in its original labelled container, and a letter from your clinic all help.

- Expect a roadside test to show cannabis. The police can use a roadside kit that screens for cannabis. It cannot tell a prescribed medicine from an illegal drug. If the police think you are unfit to drive you can be arrested and asked for a blood or urine sample at a police station.

Telling the DVLA

You must tell the DVLA if you develop a "notifiable" medical condition, or one you have gets worse. Notifiable conditions are "anything that could affect your ability to drive safely". The rule is about your condition, so check whether the condition you are being treated for is on the DVLA's list. You can be fined up to £1,000 for not telling the DVLA about a condition that might affect your driving.

Penalties

A drug-driving conviction can mean a driving ban of at least one year, an unlimited fine, up to six months in prison and a criminal record. The conviction stays on your licence for 11 years.

Northern Ireland

The over-the-limit offence does not apply in Northern Ireland, but the government's guidance says you could still be arrested there if you are unfit to drive.

This guide is general information, not legal advice. If you are stopped or charged, speak to a solicitor.
Sources
Checked on 5 October 2026. Laws and official guidance change, so read the source before you rely on anything here.
- GOV.UK: Drugs and driving: the law
- Road Traffic Act 1988, section 5A (legislation.gov.uk)
- GOV.UK: Drug driving (limits and the medical defence)
- GOV.UK: Medical conditions, disabilities and driving

From MedCannaIndex. Fees and product details are as recorded there and should be confirmed with the clinic or pharmacy. This is not medical advice: which product is suitable, and how much, is for the prescribing specialist.