Anyone who uses cannabis, even occasionally, will want to know how long it stays in their system before it’s safe to drive. What often surprises people is just how long the active compound – delta-9-tetrahydrocannabinol (THC) – can linger in the blood. Even after you feel completely sober, traces can remain for many hours, and sometimes days.
The legal limit is set very low, so it’s easy to underestimate the amount of time you need to wait before it’s safe to drive. Cannabis is now the single most common drug found in drug driving prosecutions across England and Wales.
If you would like to discuss your case, please email us at [email protected], call 0333 240 7373, or complete our online contact form.
How Long Does Cannabis Stay In Your System?
How long THC stays in your body depends on many factors:
- The strength of the cannabis.
- How it was used.
- Your size, weight, and metabolism.
There’s no reliable and precise way to predict when THC will drop below the legal limit – so the below can only be used for general guidance:
How Long After One Joint Is It Safe To Drive?
- Some studies show that in occasional users, after smoking one joint, THC can fall below the legal limit of 2 µg/L within as little as 3-6 hours. However, this period can be significantly longer when the cannabis is stronger or the person’s metabolism is slower.
- To be on the safe side, it’s best to allow at least 24 hours before driving.
How Long After Two Joints Is It Safe To Drive?
- With two joints or higher-strength cannabis, THC may stay above 2 µg/L for 12-24 hours or longer, depending on dose and frequency of use.
- Regular or heavy users can test positive for several days. THC builds up in body fat and is slowly released back into the bloodstream.
- Variations in tolerance, dosage, and body composition mean that there is no single reliable ‘safe’ timeframe – only general estimates.
‘Skunk’ v Resin in Drug Driving
Modern ‘skunk’ strains are by far the most common form of cannabis in the UK and have been grown for higher THC levels. Strength varies greatly between strains and batches, with some containing more than twice as much THC as others. In contrast, traditional resin or ‘block’ cannabis typically contains much lower THC. These differences underscore how difficult it is to predict the THC levels in a person’s body.
What is the Offence of Drug Driving in law?
Section 5A of the Road Traffic Act 1988 makes it an offence to drive, attempt to drive, or be in charge of a vehicle with a specified controlled drug in the blood above the prescribed limit.
For cannabis, the specified compound is delta-9-tetrahydrocannabinol (THC), and the prescribed limit is just 2 micrograms per litre (2 µg/L) of blood.
The offence is ‘strict liability’ – which means even if the cannabis was accidentally consumed or no longer causing any effect – a driver is guilty by virtue of simply being over the limit.
What is the Sentencing for Cannabis Drug Driving?
Sentencing depends heavily on whether there were signs of impairment, such as glazed eyes or erratic driving. Obtaining and reviewing the case papers in advance is essential in order to assess the evidence and advise on likely outcome.
Possible sentencing outcomes include:
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Mandatory disqualification and fine – At least 12 months’ disqualification, rising to a minimum of 3 years for a second offence within 10 years, plus a financial penalty.
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Community orders – Such as unpaid work or a curfew, typically where there is evidence of impairment, multiple substances, or driving a goods vehicle.
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Imprisonment – Up to 6 months in the most serious cases involving significant impairment or multiple aggravating features.
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Impact on employment and insurance – The conviction appears on a Basic DBS certificate until spent, and on Standard or Enhanced DBS checks for at least 11 years, and may affect insurance and professional driving roles.
Can I keep my Licence if Prosecuted for Cannabis Drug Driving?
There are two ways to avoid a driving ban – pleading not guilty or relying on ‘special reasons’.
A not guilty plea may be considered where it is possible to challenge whether the prosecution can prove that the driver was over the drug-driving limit at the time of driving, for example where there is an issue of post-driving consumption, or where the statutory procedures were not properly followed.
‘Special reasons’ are extenuating circumstances relating to the offence itself that may justify the court exercising its discretion not to impose a driving ban. They are not a defence in law to the charge.
If neither of these apply, it may still be possible to reduce the length of the driving ban by putting forward personal mitigation and supplying supporting documents. However, it is important to note that the minimum period of disqualification following conviction is 12 months, unless ‘special reasons’ apply.
See our Cannabis drug driving defence page for more information.
If you would like to discuss your case, please email us at [email protected], call 0333 240 7373, or complete our online contact form and a member of our motoring law team will get back to you promptly.
