Changes to drug driving law

Explains changes to drug driving law and the guidance available for healthcare professionals and users of prescription medicine.

In 2012, government announced a new offence in regard to driving with a specific controlled drug in the body above that drug’s accepted limit. The aim was to reduce expense, effort and time wasted from prosecutions that fail because of difficulties proving a particular drug impaired a driver.

Following a report from a panel of experts and a drug driving consultation the government decided to take:

  • a zero tolerance approach to 8 drugs most associated with illegal use, with limits set at a level where any claims of accidental exposure can be ruled out
  • a road safety risk based approach to 8 drugs most associated with medical uses
  • a separate approach to amphetamine that balances its legitimate use for medical purposes against its abuse

On 2 March 2015 8 generally prescription and 8 illicit drugs were added into new regulations that came into force in England and Wales. Regulations on amphetamine came into force on 14 April 2015.

Table of drugs and limits

‘Illegal’ drugs (‘accidental exposure’ – zero tolerance approach) Threshold limit in microgrammes per litre of blood (µg/L)
benzoylecgonine 50µg/L
cocaine 10µg/L
delta-9-tetrahydrocannabinol (cannabis) 2µg/L
ketamine 20µg/L
lysergic acid diethylamide 1µg/L
methylamphetamine 10µg/L
Methylenedioxymethamphetamine (MDMA) 10µg/L
6-monoacetylmorphine (heroin) 5µg/L
‘Medicinal’ drugs (risk based approach) Threshold limit in blood
clonazepam 50µg/L
diazepam 550µg/L
flunitrazepam 300µg/L
lorazepam 100µg/L
methadone 500µg/L
morphine 80µg/L
oxazepam 300µg/L
temazepam 1,000µg/L
Separate approach (to balance its risk) Threshold limit in blood
amphetamine 250µg/L

The government is unable to provide any guidance on what amounts of dosage would equate to being over the specified limits. There are too many variables, such as physical characteristics, where each person will metabolise the drug at different rates. Eating or drinking will also have an effect on the blood concentration.

How will the new laws affect you if you’re taking prescription medicines?

You should continue taking medicine(s) as advised by your doctor or healthcare professional, or according to the patient information leaflet that comes with the medicine.

The new law gives the police powers to test and arrest drivers suspected of driving after taking certain controlled drugs in excess of specified levels. It also provides a medical defence if you’re taking medicine in accordance with instructions from a healthcare professional or an accompanying leaflet, provided you’re not impaired.

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.

Drug drive: am I fit to drive? video

For further information, read about the law on drugs and driving.

Information for healthcare professionals

We’ve published guidance for healthcare professionals. Its purpose is to make sure people taking prescription and over-the-counter drugs understand the new offence and their responsibility not to drive whilst impaired.

We’ve also produced promotional materials for patients in England and Wales to help you explain the new offence to the public:

Policy, consultations and background

The drug driving consultation sought views on proposals about the drugs to be included in new legislation and the limits to be specified.

The proposals followed a report by a panel of medical and scientific experts which provided advice to the government on drug driving. The government then published a summary of responses to the consultation which concluded there was support for our proposals.

We decided to take a zero tolerance approach to 8 drugs most associated with illegal use. We also decided to take a road safety risk based approach to 8 drugs most associated with medical uses. This approach was included in regulations presented to Parliament and regulations then came into force in March 2015. A separate approach to amphetamine that balances its legitimate use for medical purposes against its abuse was presented to Parliament and regulations came into force on 14 April 2015.

  1. Drug driving law evaluation

    • Research and analysis
  2. Review of oral fluid: alternative biological matrices for drug driving

    • Research and analysis
  3. Drug driving: amphetamine limit

    • Consultation outcome
  4. Proposed regulations for drug driving

    • Consultation outcome
  5. Enforcement procedures against drink drivers and other offenders

    • Consultation outcome
  6. Driving under the influence of drugs

    • Independent report
  7. Government response to drink and drug driving reports

    • Policy paper


Published 24 July 2013
Last updated 27 August 2017 + show all updates
  1. Drug driving law evaluation.
  2. Proposed new drug driving law - guidance for healthcare professionals and advice for people taking prescription medicines.
  3. First published.