UK drug driving guide: Limits, penalties, and how a charge can be challenged

A positive roadside drug test isn't a conviction. And neither is a blood result over the limit.

If you've been stopped by police, swabbed and asked for a blood sample, you've probably been told to expect a 12-month driving ban.

It's a frightening place to be, and you're not the only one who's probably panicking a bit. Many people in your position plead guilty at the first hearing because they assume the number on the lab report settles everything. It doesn't.

That number is the last link in a chain that starts at the roadside, and there are rules the police and laboratories must follow at every stage. Understanding drug driving laws in the UK means following that chain from stop to sentence.

This guide takes you through it, stage by stage.

At a glance

• A drug driving conviction carries a minimum 12-month driving ban, an unlimited fine, and up to six months in prison.
• Your sentence depends mainly on signs of impairment and how you were driving, not on how far over the limit you were.
• Every stage of the evidence, from the roadside swab to the laboratory report, can be checked.
• Free initial advice from a specialist drug driving solicitor: call 0151 422 8020.

What counts as drug driving under UK law?

Three different drug driving offences can follow a drug driving stop. The prosecution needs different evidence for each one. Knowing which offence you've been charged with is the first step in your defence.

Driving over a specified limit (section 5A). Since 2 March 2015, it's been an offence under section 5A of the Road Traffic Act 1988 to drive, attempt to drive, or be in charge of a motor vehicle with more than the legal limit of a specified drug in your blood.

This is known as a strict liability offence. Put simply, the prosecution doesn't have to prove the drug affected your driving. Only that the level in your blood was above the legal limit. Most drug driving charges fall under this section.

Driving while unfit through drugs (section 4). For this offence, the prosecution must prove that drugs affected your ability to drive safely. It can apply to any drug, whether legal or illegal drugs, including drugs that don't have a specific limit.

That's why drivers accused of using laughing gas are charged under section 4, because nitrous oxide has no specified limit of its own.

Failing to provide a specimen (section 7(6)). Refusing to give a blood or urine sample without a reasonable excuse is a separate offence, carrying a mandatory driving ban of its own. We explain this in more detail in the sections on the police stop and penalties.

Driving or "in charge"? Each offence can also apply if you were "in charge" of a vehicle rather than actually driving it. For example, you might have been sitting in a parked car with the keys. The penalties are lower, and there's a specific defence, both covered later in this guide.

This guide covers the law in England and Wales. Scotland sets its limits in separate regulations, and the drug driving limits don't apply in Northern Ireland.

What are the drug driving limits?

The law sets limits for 17 drugs, measured in micrograms per litre of blood (µg/L).

For drugs mainly linked to illegal use, the government took a near-zero-tolerance approach. The limits were set just high enough to avoid catching people who may have been exposed accidentally.

For medicines, the limits are higher than the levels normally found in people taking them as prescribed. Amphetamine has its own limit, because it's both prescribed and misused.

Drug	Type	Limit (µg/L of blood)
Lysergic acid diethylamide (LSD)	Illegal	1
Delta-9-tetrahydrocannabinol (THC, cannabis)	Illegal	2
6-monoacetylmorphine (heroin)	Illegal	5
Cocaine	Illegal	10
Methylamphetamine	Illegal	10
MDMA	Illegal	10
Ketamine	Illegal	20
Benzoylecgonine (BZE, from cocaine)	Illegal	50
Clonazepam	Medicine	50
Morphine	Medicine	80
Lorazepam	Medicine	100
Amphetamine	Medicine (separate approach)	250
Flunitrazepam	Medicine	300
Oxazepam	Medicine	300
Methadone	Medicine	500
Diazepam	Medicine	550
Temazepam	Medicine	1,000

Source: GOV.UK, drug driving limits

Why you can't calculate a "safe" time to drive. The government says it can't tell you what dose would put you over a limit. There are too many variables, from how your body processes a drug to what you've eaten. Cannabis is the clearest example. THC can stay above the 2µg/L cannabis limit long after its effects have worn off, especially in regular users. The same uncertainty runs through cocaine drug driving charges, where the limit is just 10µg/L.

Why cocaine can count twice. Your body breaks cocaine down into benzoylecgonine (BZE), which has its own limit and stays in your blood far longer than cocaine itself.

What if you take prescribed medicine? A prescription doesn't make you immune, but there's a medical defence if you followed your prescriber's advice, explained in the defences section below. Some medicines cause more problems than others. Opioid painkillers and benzodiazepines are among the prescription medicines that can affect your licence, and in rare cases ADHD medication can produce a misleading drug test result.

What happens if the police stop you?

The roadside swab is a screening test, not evidence. The evidence against you is the sample taken later — and the rules for taking it are strict.

When can the police test you? Under section 6 of the Road Traffic Act 1988, police can carry out preliminary tests if they reasonably suspect you have drugs in your body. They can also test you after a moving traffic offence or an accident.

The roadside swab. Police use a saliva device, often called a DrugWipe, that screens only for cannabis and cocaine. A positive swab usually leads to arrest. A negative one doesn't always end things. Officers can still carry out a Field Impairment Test, a set of balance and coordination checks used to judge whether drugs have affected you. Swabs are screening tests only, so they can't be used to prove the offence in court, and roadside drug tests can give false positives.

The evidential sample. After arrest, you'll be asked for a blood or urine sample at the police station, usually blood taken by a healthcare professional. In relevant cases, the sample is split, and part of it may be made available to you for independent analysis.

Refusing a sample. Saying no without a reasonable excuse is a crime in its own right, called failing to provide, and it carries a mandatory driving ban. The excuse must be genuine, such as a medical condition that makes giving blood unsafe. A genuine needle phobia can count as a reasonable excuse for refusing a blood test.

What happens after you're arrested for drug driving?

In most cases, you'll be released under investigation while your blood is analysed. That waiting period is when evidence can be preserved, so it's the best time to get advice, not a time to sit and wait.

Released under investigation (RUI) means you're free to go without being charged while the police wait for your results. Laboratory analysis often takes several months.

Evidence can disappear in that time. Custody CCTV and body-worn video are often kept for limited periods only. If you've been released under investigation for drug driving, a solicitor who contacts the police early can ask for that footage to be preserved before it's lost.

The charge. If your result comes back over the limit, you'll usually receive a postal requisition (the letter charging you) with a date for your first hearing at the magistrates' court.

The plea. At that hearing, you'll be asked to plead guilty or not guilty. A not guilty plea means the prosecution has to serve its evidence, including the details behind your laboratory result. A guilty plea means nobody ever checks it.

Don't wait to be charged. Call 0151 422 8020 for free advice — there's no obligation.

What are the penalties for drug driving in the UK?

If you're convicted of driving over a specified limit, drug driving sentencing guidelines state a court must ban you from driving for at least 12 months. It can also fine you, impose a community order, or send you to prison for up to six months.

Since 1 July 2023, magistrates have followed a definitive sentencing guideline for this offence. It places your case in one of three categories, based on two questions:

• How culpable were you? Higher culpability means you were driving a goods vehicle or bus, driving for commercial purposes, or had another specified drug or alcohol in your body.
• How much harm was there? Greater harm means there were obvious signs of impairment, or evidence of an unacceptable standard of driving.

How far over the limit you were doesn't decide your category. The guideline says there's no direct link between the level of a drug and the harm caused.

Category	When it applies	Starting point	Range	Driving ban (first offence)
1	Higher culpability and greater harm	12 weeks' custody	High-level community order to 26 weeks' custody	29 to 36 months
2	Higher culpability and lesser harm, or lower culpability and greater harm	Medium-level community order	Low-level to high-level community order	17 to 28 months
3	Lower culpability and lesser harm	Band C fine (around 150% of weekly income)	Band B fine to low-level community order	12 to 16 months

Source: Sentencing Council. These drug driving sentencing guidelines aren't fixed outcomes, and the court can move up or down a range depending on the facts of your case.

Repeat offences. If you were convicted of drink driving, drug driving, or failing to provide in the 10 years before this offence, the minimum ban rises to three years.

Being in charge. If you weren't driving but were in charge of the vehicle, the court can impose 10 penalty points or a discretionary ban, and the maximum sentence is three months' custody.

Failing to provide. Refusing a sample in a drug driving case also carries a mandatory ban of at least 12 months.

Can hardship save your licence? No. Exceptional hardship arguments only apply to bans for collecting 12 or more penalty points. They can't stop a mandatory drug driving ban. After a conviction, the only way to avoid the ban is special reasons, explained below.

[Editor's note: add a link to the penalty points and bans pillar here once it is live.]

What are the wider consequences of a drug driving conviction?

The ban ends. The conviction doesn't.

A drug driving conviction is a criminal conviction, and it shows on your driving licence record for 11 years. Over that time, it can affect:

• Insurance. Expect higher premiums once you're back on the road.
• Work. If you drive for work, your employer will see the conviction on your licence. It can also appear on DBS checks, depending on the type of check and how long ago you were convicted.
• Licences and regulated jobs. Taxi and HGV licensing, and some professional regulators, may require you to declare it.
• Travel. Some countries, including the USA, can make entry harder for people with drug convictions.

That's 11 years of consequences from a ban that, for a first offence, usually lasts one to three.

How can a drug driving charge be challenged?

Each stage you've just read about comes with procedures the police and the laboratory must follow. A check doesn't guarantee a result. But if nobody checks, nobody finds the problem. In a single year, the M.A.J. Law team won 132 drug driving cases, and these are the defences it fights with.

Was the procedure followed?

Police record the evidential procedure on forms from the Manual of Guidance on Drink and Drug Driving, known as the MGDD/B. The forms show what you were told, when the sample was required, who took it, and how it was handled. A mistake on a form doesn't end a case on its own. But where the paperwork, custody records, and video footage don't match, or the sample can't be accounted for from your arm to the laboratory, police errors in the MGDD/B procedure can undermine the result.

Is the laboratory result reliable?

Drug analysis is harder than alcohol analysis, with a wider margin of uncertainty. Results are reported as a "not less than" figure to allow for measurement uncertainty.

The first report you'll usually see is a Streamlined Forensic Report, or SFR1, a short summary of the result. If the defence doesn't accept it, the prosecution must provide a fuller report, the SFR2. Your solicitor can also ask for the analytical data behind the result, so an independent expert can check how the sample was tested.

Laboratories do get it wrong, and there are often opportunities to challenge forensic evidence in a drug drive case. Between April 2019 and December 2020, the laboratory Synlab reported 1,778 blood samples as over the limit. Every one of those results was later rescinded after a quality failure.

Does the medical defence apply?

If you were prescribed a specified drug, including through a medical cannabis prescription, section 5A(3) gives you a defence where you took it in line with your prescriber's advice and the instructions supplied with it, including any advice on how long to wait before driving. Once you raise enough evidence to support the defence, the prosecution has to disprove it beyond reasonable doubt. The defence doesn't apply to a section 4 "unfit" charge, so you still mustn't drive if your medicine impairs you.

Did you take the drug after driving?

The law assumes the level in your sample was no lower than when you were driving. The post-driving consumption defence displaces that assumption if you prove, on the balance of probabilities, that you took the drug after you stopped driving, and that without it you'd have been under the limit. This usually needs a report from an expert toxicologist.

In one M.A.J. Law cannabis case, the client had admitted smoking cannabis about three hours before driving. His blood reading was 6.1µg/L, more than three times the limit. Before his blood test, he'd also eaten cannabis while sitting in the police car. His expert report was excluded at the magistrates' court, and he was convicted. On appeal at the Crown Court, the report was admitted, the court accepted his account, and he won his appeal, with costs awarded.

Are there special reasons?

Special reasons don't stop a conviction, but they can persuade the court not to ban you. They must relate to the offence itself, not your personal circumstances. Examples include food or drink that was spiked without your knowledge, or inhaling cannabis smoke without knowing, for instance while you were asleep. Expert evidence is usually needed.

Were you only in charge?

If you're charged with being in charge rather than driving, it's a defence to prove there was no likelihood of you driving while you were still over the limit.

Drug driving FAQs

Can I keep driving while I'm released under investigation?

In most cases, yes. A ban only starts if you're convicted, unless bail conditions say otherwise. But if a drug is still in your system, a second stop could lead to a second charge.

Can CBD products put me over the limit?

Some CBD products contain traces of THC, the substance the cannabis limit measures. Regular use could, in some cases, produce a detectable level. If you use CBD and have been charged, keep the packaging and get advice before assuming anything about your result.

Does a drug driving conviction show on a DBS check?

It can. Whether it appears depends on the type of check and how long ago you were convicted. Your driving licence record will show it for 11 years either way.

What should you do before you plead?

The number on your laboratory report feels final. It isn't the whole case.

It's the last link in a chain that runs from the roadside, through the custody suite, to a laboratory you'll never see. Every link has to hold for the prosecution to prove its case. Plead guilty at the first hearing, and none of those links is ever tested. Ask the questions first, and you'll know where you stand before you decide.

M.A.J. Law fights drug driving cases across England and Wales, from the first call to the final verdict. Call 0151 422 8020 for free initial advice — there's no obligation.