Drug driving limits: knowing the law

We all know the laws on drink driving, but it seems we’re not so clear on drug driving. Drug driving doesn’t just involve illegal drugs, but also some prescription drugs over prescribed levels.

With more than 5% of motorists admitting to driving while under the influence of drugs, it’s important to understand what the legal limits and penalties are.

 

We all know the laws on drink driving, but it seems we’re not so clear on drug driving. Drug driving doesn’t just involve illegal drugs, but also some prescription drugs over prescribed levels.

With more than 5% of motorists admitting to driving while under the influence of drugs, it’s important to understand what the legal limits and penalties are.

 

Daniel Hutson
Motor insurance expert
3
minute read
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Posted 6 NOVEMBER 2019 Last Updated 14 MARCH 2022

What are the drug driving laws? 

Drug driving legislation covers both legal and illegal drugs. It’s against the law to drive if you’re unfit to do so because of drugs – whether they’re prescribed or illegal. And having certain levels of illegal drugs in your blood makes it an offence to get behind the wheel, even if they haven’t affected your driving.

Illegal drugs 

You could be arrested and charged if you’re found to be over the drug-drive limit for specific substances. The limits are very low but aren’t set at zero to allow for ‘accidental exposure’ – for instance, if you inadvertently inhale cannabis smoke in a public place through no fault of your own. 

Below is a table of some of the most common illegal recreational drugs and their allowable limits:

Drug name

Threshold limit in micrograms per litre of blood (µg/L)

Benzoylecgonine (metabolite of cocaine)

50

Cannabis

2

Cocaine

10

Heroin

5

Ketamine

20

Lysergic acid diethylamide (LSD)

1

Methylenedioxymethamphetamine (MDMA)

10

Methylamphetamine

10

Prescription medicines 

It’s against the law to drive if legal drugs impair your driving. It’s also illegal if you have certain drugs that are above specified limits in your blood and you haven’t been prescribed them. 

Below is a table of the prescription drugs covered by the law, along with their limits:

Drug name

Threshold limit in blood (µg/L)

Amphetamine e.g. dexamphetamine or selegiline

250

Clonazepam

50

Diazepam

550

Flunitrazepam

300

Lorazepam

100

Methadone

500

Morphine or opiate and opioid-based drugs e.g. codeine, tramadol or fentanyl

80

Oxazepam

300

Temazepam

1,000

You can drive after taking these drugs, but they must be prescribed to you. Sedatives and stimulants can affect your ability to drive, so talk to your doctor or pharmacist about whether it’s safe to get behind the wheel. 

Although these laws don’t apply in Northern Ireland, you could still be arrested if you’re unfit to drive. 

Top tip

Carry evidence of your prescription with you in case you’re stopped by the police.

How do drugs affect your ability to drive? 

Just as driving with alcohol in your system can be dangerous, driving under the influence of drugs can also be unsafe. Don’t underestimate the effects of them, even if they’re prescribed medicines. If you’re in doubt, it’s best to avoid driving while on drugs altogether.

If you drive while unfit, you could have: 

  • Slower reaction times
  • Impaired co-ordination
  • Blurred vision
  • Over-confidence
  • Loss of concentration
  • Increased risk-taking behaviour
  • A tendency for inappropriate driving
  • Inability to judge distances and speeds properly.

What happens if I’m stopped for drug driving? 

Police can stop drivers and make them do a ‘field impairment assessment’. This means they might ask you to prove you can walk in a straight line or touch your nose with your eyes closed. 

Officers have also been issued with roadside drug-testing kits to do immediate spot checks for levels of cannabis or cocaine in the blood. People suspected of having high levels of other substances will have to do more tests at a police station.

What are the penalties for drug driving? 

Not surprisingly, the penalties are severe if you’re caught driving while under the influence. Being convicted of a drug driving offence could result in: 

  • A minimum one-year driving ban
  • An unlimited fine
  • Up to six months in prison
  • A criminal record
  • A conviction notification on your driving licence, which will last for 11 years
  • Up to 14 years in prison if you cause death by dangerous driving under the influence of drugs. 

A drug driving conviction could also mean: 

  • Trouble getting a visa for travelling to countries, including the USA.
  • Losing your job if you drive for a living.

Will a drug driving conviction affect my car insurance? 

If you’re found guilty of a drug driving offence, you’ll probably see the cost of your motor insurance rise sharply. If you do have a conviction, you must tell your insurance provider about it. 

If you have a driving ban, it may be a good idea to cancel your insurance, take your car off the road and make a Statutory Off Road Notification (SORN) while the ban lasts.

Once you’re allowed to drive again, you might find it difficult to find cover as many insurance providers refuse to insure those with drug driving convictions. However, there are specialist insurance providers who could provide you with cover. You’ll just need to accept that it’s probably going to cost a lot more than it did before. See our guide to convicted drivers insurance.

You can make a start by comparing car insurance with us. Just give us details about you, your car and any convictions.

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