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Alcohol and driving

When we drink alcohol it affects our ability to drive, even if we don’t feel any different. 

Even small amounts of alcohol impacts our central nervous system, affecting:

  • reaction times
  • coordination
  • concentration
  • judgement
  • vision

Your ability to drive is affected and you are twice as likely to have a fatal collision, even below the legal limit.

Blood alcohol concentration 

Blood alcohol concentration (BAC) is a measurement of the amount of alcohol in our blood.

If you’re stopped by a member of An Garda Siochana, they will test you using a breath test. If you fail this test, you will be asked to take another, more accurate test, usually in the Garda Station. 

The legal BAC limit is 0.05 for most drivers and 0.02 for professional, learner and novice drivers. Most people will be over this limit after one standard drink.

A standard drink contains 10mg of alcohol. Here are some examples: 

Standard drink

Find out more about standard drinks and low-risk weekly drinking guidelines. 

When is it safe to drive again after drinking alcohol

For most people, it takes about one hour for the body to process a standard drink.

So, for example, if you drink 5 glasses of beer, 5 small glasses of wine, or 5 single measures of spirits you would need to wait at least five hours before it is safe to drive.

However, there are a lot of things that affect the way your own body absorbs and processes alcohol so it is difficult to say exactly how long you should wait before you drive.

These factors include:

  • how much you’ve had to eat
  • if you’re tired
  • if you’ve taken any prescription medicines or other drugs
  • your gender, weight and height

Your ability to drive will also depend on whether you’ve had enough sleep.

Your BAC will continue to rise for up to three hours after you've stopped drinking, as your system absorbs the alcohol from your stomach into your blood stream.

Drinking water or coffee, eating or having a shower will not make the alcohol in your blood disappear any faster. Only time can do that.


Home breathalyser kits are not reliable for the following reasons:

  • the results can be different from the results given by the breathalysers used by An Garda Siochana
  • your body absorbs alcohol from the stomach over time, so a breathalyser might give a pass result at one time and a fail result a short time later
  • a breathalyser is a screening device and the true test is the one carried out in the Garda Station using blood or urine 

Prescription medicines and illegal drugs

If you have taken any illegal drugs you should not drive.

If you are taking prescription medicines or other drugs, follow the advice in the information leaflet in the packet. If in doubt, check with a pharmacist or doctor.

Read more about alcohol's interactions with medicines and other drugs. 

Plan ahead and avoid drinking and driving

  • have a designated driver
  • research your public transport options before you go out
  • budget for a taxi
  • have a backup plan for getting home – a friend or parent you can call
  • arrange a lift
  • arrange to stay overnight
  • do not accept a lift from someone who has been drinking
  • make alternative transport arrangements for the next day

For more about driving and alcohol, see the Road Safety Authority –
Use our Drinks Calculator to find out if alcohol is impacting your health, weight and wallet.

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