How Long After Smoking Weed Can You Drive?

VAPE GUIDEs

VAPE TIPS

VAPE HELP

How Long After Smoking Weed Can You Drive in the UK?

In the UK, driving after smoking cannabis is illegal if the level of THC (tetrahydrocannabinol) in your system exceeds the legal limit, regardless of whether you feel “high” or not. THC is the psychoactive compound in cannabis, and even low levels can lead to a drug-driving conviction.

The legal limit for THC in the bloodstream is 2 micrograms per litre (µg/L)—a level set so low that it can register even after the effects have worn off. There is zero tolerance for recreational cannabis use behind the wheel.

How Long Does THC Stay in Your System?

THC affects everyone differently, but as a general guide:

  • If you smoke occasionally, THC can stay in your blood for up to 24–48 hours

  • If you smoke regularly, it can remain in your system for up to a week or more

  • In urine, THC metabolites can be detected for days to weeks, but blood tests (used for roadside enforcement) are focused on recent use

THC is fat-soluble, meaning it binds to your body’s fat stores and is slowly released over time. This makes it harder to give a one-size-fits-all answer.

So, How Long Should You Wait Before Driving?

There’s no official “safe” time limit, but most experts recommend:

  • At least 24 hours after smoking a small amount

  • 72 hours or more if you're a regular user or used a high-THC strain

  • Longer if you used edibles, as these stay in your system longer than smoked cannabis

Just because you no longer feel high doesn't mean THC is out of your blood.

Penalties for Drug Driving in the UK

If you’re caught driving with more than the legal limit of THC in your system, you could face:

  • A minimum 12-month driving ban

  • An unlimited fine

  • Up to 6 months in prison

  • A criminal record

  • Increased insurance costs

  • Potential job loss if driving is part of your role

Police can stop you and conduct a roadside saliva drug test or a field impairment assessment. If you fail, you'll be taken to a police station for a blood test to confirm THC levels.

What About Medical Cannabis?

Even if you have a medical cannabis prescription, you can still be prosecuted for drug driving if:

  • THC levels are above the legal limit, and

  • Police believe your driving is impaired

You may be protected only if you are not impaired and can prove legal medical use. The law is strict, and being prescribed cannabis does not give you a free pass to drive with THC in your system.

Can You Drive After Using CBD?

CBD (cannabidiol) is a non-psychoactive compound and is legal in the UK if it contains less than 1mg of THC per container. However, not all CBD products are properly regulated. Some may contain enough THC to show up in a drug test.

If you use CBD and are concerned about driving, always buy from a reputable supplier that provides lab reports and verifies THC content.

Factors That Affect How Long THC Stays in Your Body

Several things influence how long THC remains detectable:

  • Frequency of use – Regular users store more THC in fat tissue

  • Dosage and strength – High-potency strains leave stronger traces

  • Body fat and metabolism – More fat = more THC stored

  • Method of use – Edibles take longer to process than smoked or vaped cannabis

  • Hydration and physical activity – May impact how quickly THC is flushed out

Because of this, two people could smoke the same joint and test positive for very different lengths of time.

The Bottom Line

There is no safe or guaranteed time frame for driving after smoking weed in the UK. THC can remain in your system for longer than you might think, and the legal limit is extremely low.

To stay on the right side of the law—and keep yourself and others safe—the most reliable advice is simple: don’t drive at all for at least 24 hours after using cannabis, and longer if you’re a frequent user. If in doubt, don’t risk it.