Drug driving: specified limits, unfitness and the medical defence
Driving or attempting to drive with a specified drug above its limit (Road Traffic Act 1988 s.5A), or while unfit through drugs (s.4), is a summary offence carrying up to 6 months' imprisonment, an unlimited fine and a mandatory ban of at least 12 months, or 3 years for a second relevant conviction within 10 years. Medicines prescribed and taken as directed have a statutory defence under s.5A(3).
The offences
- Driving or attempting to drive with a specified controlled drug above the specified limit (s.5A(1)(a), (2)). No impairment needs to be proved.
- Being in charge above the limit (s.5A(1)(b)); it is a defence to prove there was no likelihood of driving while still over it (s.5A(6)).
- Driving or being in charge while unfit through drugs (s.4). Impairment must be proved; any drug counts, including medicines.
The limits
The Drug Driving (Specified Limits) (England and Wales) Regulations 2014 set limits in microgrammes per litre of blood. Illegal drugs are near zero: cannabis (THC) 2, cocaine 10, benzoylecgonine (a cocaine by-product) 50, ketamine 20, MDMA 10. Medicines have higher, risk-based limits: amphetamine 250, diazepam 550, methadone 500, morphine 80, temazepam 1,000.
The medical defence
Under s.5A(3) it is a defence that the drug was prescribed or supplied for medical or dental purposes, taken in accordance with the prescriber's directions and any manufacturer's instructions, and lawfully possessed. It is lost if advice or instructions on how long to wait before driving were ignored (s.5A(4)). Once raised, the prosecution must disprove it beyond reasonable doubt (s.5A(5)). It does not apply to s.4.
Testing and evidence
Police may require a roadside saliva test (s.6C), which currently screens for cannabis and cocaine. A positive result can lead to arrest and a blood specimen (s.7(3)). Failing without reasonable excuse to provide a specimen (s.7(6)) carries the same penalties and ban as the driving offence where the specimen related to driving or attempting to drive.
Penalties
Driving or attempting to drive (s.5A or s.4(1)), and failing to provide when driving: up to 6 months' imprisonment, an unlimited fine and a mandatory ban of at least 12 months (Road Traffic Offenders Act 1988 s.34), rising to 3 years after a relevant drink or drug driving conviction in the previous 10 years. Being in charge: up to 3 months and a £2,500 fine, with 10 points or a discretionary ban. For adults convicted from 22 March 2026, prison terms of 12 months or less are presumed suspended, subject to exceptions (Sentencing Act 2026 s.1). Unlike drink driving, no rehabilitation course reduction is available for a s.5A ban or a s.4 ban for unfitness through drugs (s.34A).
Sentencing guideline
The s.5A guideline ranges from a Band B fine to 26 weeks' custody. Higher culpability: commercial or goods-vehicle driving, or another drug or alcohol present. Greater harm: obvious impairment or an unacceptable standard of driving. Category 1 starts at 12 weeks' custody with a 29-36 month ban; category 3 at a Band C fine with 12-16 months.
In practice
Procedure and special reasons mirror the alcohol offences (see Drink driving, failing to provide and drug driving and Exceptional hardship, special reasons and new drivers). Early advice matters where a medicine was prescribed or the procedure is challenged.
Authorities: Road Traffic Act 1988 ss.4, 5A, 6B, 6C, 7, 11; Drug Driving (Specified Limits) (England and Wales) Regulations 2014 (SI 2014/2868) reg.2, as amended by SI 2015/911; Crime and Courts Act 2013 s.56 (51 weeks read as 6 months); Road Traffic Offenders Act 1988 ss.34, 34A and Sch.2 Pt I; Sentencing Council, Driving or attempting to drive with a specified drug above the specified limit guideline (effective 1 July 2023); CPS, Road Traffic - Drink and Drug Driving legal guidance; gov.uk, Drugs and driving: the law; Sentencing Act 2026 s.1