Driving is something many of us do every day, often without thinking too much about it. But alcohol and drugs can change how we think, react, and make decisions in ways that are not always obvious at the time. Feeling “fine” does not always mean it is safe, or legal, to drive.
Drink and drug driving are criminal offences in the UK because of the serious risk they pose to drivers, passengers, pedestrians, and other road users. Every year, thousands of people are killed or seriously injured in collisions linked to alcohol or drug use.
This page explains how alcohol and drugs affect driving, what the law says, how testing works, and why planning ahead matters.
How alcohol affects driving
Alcohol is a depressant. It slows down the brain and nervous system, affecting many of the skills needed to drive safely.
After drinking alcohol:
- reaction times slow, meaning it takes longer to brake or respond to hazards
- judgement is impaired, making it harder to assess speed, distance, and risk
- concentration drops, especially on longer or unfamiliar journeys
- coordination and vision are affected, reducing control of the vehicle
Alcohol can also increase confidence and risk-taking behaviour, which may lead to speeding, unsafe overtaking, or misjudging road conditions.
Even small amounts of alcohol can have an impact. Being under the legal limit does not mean driving is safe.
How drugs affect driving
Drugs affect people in different ways depending on the substance, dose, frequency of use, and the individual. Both illegal drugs and prescribed medicines can impair driving.
Drugs may:
- slow reaction times and decision-making
- affect coordination and balance
- distort perception and judgement
- cause drowsiness, confusion, or agitation
Some drugs wear off quickly, while others remain in the body for much longer. Certain substances can still be detected days after use, particularly with frequent or long-term use.
Prescribed medicines, including some painkillers, benzodiazepines, and opioid treatments, can also affect driving, especially when first started, when doses change, or when combined with alcohol or other drugs.
The law on drink and drug driving
In England, Scotland and Wales, it is illegal to drive if:
- you are unfit to drive because of alcohol or drugs, or
- you have over the specified legal limits of certain substances in your body
For alcohol, the legal limits are different in Scotland compared to England and Wales. For drugs, the law sets specific blood limits for certain substances, including cannabis, cocaine, ketamine, MDMA, heroin metabolites, and some prescribed medicines.
Importantly, these laws work alongside each other. Being below a set limit does not automatically make driving legal if your driving is affected.
Northern Ireland has different legislation for drug driving, but drivers can still be arrested if unfit to drive.
Prescription medicines and driving
Some people worry that being prescribed medication means they cannot legally drive. This is not always the case.
You may be allowed to drive if:
- the medication has been prescribed to you
- you are taking it exactly as advised by a healthcare professional
- it is not affecting your ability to drive safely
However, it is illegal to drive if a prescribed or over-the-counter medicine impairs your driving.
If you are unsure, speak to your doctor, pharmacist, or prescriber. Never assume it is safe to drive just because a drug is legal or prescribed.
Testing for alcohol and drugs
Police can stop any vehicle at their discretion.
If alcohol is suspected, officers may ask you to take a roadside breath test. If this test is failed, you will be taken to a police station for further testing. Blood or urine samples may be taken if required.
If drug use is suspected, officers may carry out a field impairment assessment and use roadside drug screening kits. Blood tests are used to confirm drug levels.
Refusing to provide a sample is a criminal offence and carries similar penalties to being over the limit.
Detection times and “the morning after”
One of the most common misunderstandings is how long alcohol and drugs stay in the body.
Alcohol is usually processed at around one unit per hour, but this varies widely. Drugs vary even more. Factors that affect elimination include:
- body size and composition
- age and metabolism
- sex
- dose and frequency of use
- type of substance
- whether food was eaten
There is no reliable way to calculate when someone will be under the legal limit. Many people are caught drink or drug driving the morning after using substances the night before.
If you are unsure, the safest option is not to drive.
Penalties and wider consequences
Being convicted of drink or drug driving can have life-changing consequences.
Penalties can include:
- a minimum one-year driving ban
- unlimited fines
- imprisonment
- a criminal record
If someone is killed as a result of drink or drug driving, the maximum penalty is life imprisonment.
Beyond the court process, a conviction can:
- make car insurance extremely expensive
- affect employment, especially driving roles
- cause difficulties travelling abroad, including to countries like the USA
Planning ahead and staying safe
There is no safe or reliable way to drink or take drugs and still drive.
The safest advice is simple:
If you are driving, do not drink alcohol or take drugs, including the morning after use.
Ways to plan ahead include:
- choosing a designated driver
- using public transport or taxis
- arranging lifts with someone who is substance-free
- choosing alcohol-free drinks
Planning ahead protects you, your passengers, and everyone else on the road.
Support from Wirral Ways
If alcohol or drug use is affecting your safety, driving, or daily life, you are not alone.
Wirral Ways offers confidential, non-judgemental support, including:
- advice around alcohol and drug use
- harm reduction information
- support to cut down or stop using substances
- access to treatment and recovery support
Getting information or asking for help does not mean you are in trouble. It means you are taking steps to look after yourself and others.
Last Updated on 9 February 2026