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Drug driving limits calculator

Find out how your medication could impact your ability to drive

When it comes to ‘driving under the influence’ many drivers wouldn’t consider their hay fever medication as being particularly dangerous. But some prescription medicine affects your driving and reaction times.

However, the rules are never that straightforward, leaving many confused as to what medication you’re able to take and still be able to drive.

Our drug-driving limits calculator looks at the legal limits for driving after taking common over-the-counter and prescription medications and legal stimulants.

Need more help?

What prescription drugs can you not drive on?

The legal limits for driving under the influence of prescription drugs depends on the drug. Our calculator includes some of the more common prescription drugs. Pick one from the list to find out the legal driving limit.

What are the penalties for drug driving?

The penalties for driving under the influence of legal drugs can vary but convictions can result in automatic disqualification from driving for 12 months. After being disqualified from driving, you may find fewer and mainly expensive options when looking for car insurance.      

It’s illegal to drive in the UK under the influence of any drug that impairs your ability to drive. The rules apply to both legal and illegal drugs. Even if your ability to drive is unaffected, there is legal limit to the amount of some prescription and non-prescription legal drugs allowed in your system.

It may sound a bit strange for there to be an allowable limit for illegal drugs but there is a low allowable driving limit in case of accidental exposure. For example, for the illegal Class A drug cocaine, it’s 10 micrograms per litre of blood.

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