How Many Units of Alcohol Can You Drink and Still Drive Legally in the UK?

Don’t drink and drive!

If you’re heading out for a night on the tiles and wondering if you should take your car keys, the answer is no. The drink drive limit in the UK is incredibly strict, and the safest thing you can do if you’re planning to drink is not drive.

But if you’re the designated driver and you’d like to have a low-alcohol beer while your friends drink the real stuff, you’ll need to know how much you can drink and drive. 

Here, we help you understand what is the legal limit for alcohol, what influences the alcohol levels in your body, and the penalties you might face if you get caught drinking and driving.

What are alcohol units?

Alcohol units help us make sense of the gap between having a drink that is light on alcohol, such as a low-alcohol beer, and something heavier, like a glass of red or a Long Island iced tea. 

A unit of alcohol is defined as 8g or 10ml of pure alcohol. This means a low-alcohol beer of 1.2% ABV clocks in at only 0.6 units of alcohol. In comparison, one Long Island Iced Tea contains at least two units of alcohol. 

They’re both only one drink, but that iced tea packs far more of a punch.

How many units of alcohol can I drink and still drive?

It always bears repeating that the safest way to drive involves no alcohol.

However, in answering how many units are over the limit, it is generally estimated that the drink-drive limits in England, Wales and Northern Ireland would allow men the equivalent of 4 units of alcohol. This is around two pints of normal-strength beer. 

On the other hand, women may be able to drink three units of alcohol and remain under the limit. This is about one large glass of wine or a little more than a pint of regular-strength beer.

Here is a breakdown of some of the most common drinks and how many units they amount to:

Beer:

  • A pint of 3.8% ABV (alcohol by volume) lager is 2.2 units
  • Half a pint of 3.8% ABV lager is 1.1 unit
  • A pint of 5.2% ABV lager comes in at 3 units
  • A 660 ml bottle of 3.8% ABV lager is 2.5 units
  • A 440 ml can of cider with 5.5% ABV is 2 units

Wine:

  • A 250 ml (standard cup measure) of 11% ABV wine is 2.8 units
  • A 750 ml bottle of 11% ABV wine is 8.4 units
  • A 125 ml glass of sparkling wine is 1.5 units

Spirits and mixers:

  • A single 25 ml shot of spirits is 1 unit — this could be a gin and tonic or vodka soda.
  • A 275 ml Alcopop of 4% ABV is 1.1 units.

Alcohol units, while a useful starting point, only tell half the story. 

Many factors influence how alcohol is absorbed by our bodies, which means a large glass of wine may leave one person under the limit. Meanwhile, the same drink could tip another person over the legal limit and into dangerous territory.

What influences the alcohol levels in your body?

There are several factors that can influence your alcohol levels, including:

  • Sex, body type and metabolism.

The differing guidelines on how much men and women can drink is not accidental.

Those assigned female at birth tend to be smaller than those assigned male, which means that they often have less tissue available to absorb alcohol. In addition, women tend to have lower levels of dehydrogenase, the enzyme that breaks down alcohol before it reaches the bloodstream.

Furthermore, fitness levels and your body’s fat-to-muscle ratio also have a part to play. Muscle has more water than fat, which means alcohol is diluted more in people with more muscle tissue.

  • Medications.

Alcohol is, strictly speaking, a drug. As such, it can interact with other medications you may be taking, exaggerating the impact of any alcohol you consume. It’s always a good idea to check in with your doctor to see if drinking is allowed with your particular medication.

  • Tired, hungry and dehydrated?

Your mum was right. A full stomach does make a difference on a night out. Eating before you drink means that alcohol absorption is slowed (although not stopped). 

Similarly, being dehydrated means there’s less water in your blood to dilute alcohol. This will also increase the effects of the alcohol on your body, and your blood alcohol concentration will rise quicker.

Finally, the more tired you are, the less efficient your liver is at processing alcohol, so it stays in your system for longer. 

  • Carbonation.

The alcohol in bubbly drinks such as beer and sparkling wine is more easily absorbed into the bloodstream than in non-carbonated options like red wine or alcohol mixed with water or fruit juice.

Can I drive after drinking 2 units of alcohol?

While two units of alcohol may keep you under the legal limit should you be breathalysed on the road, that’s not to say you can neck a pint and immediately hit the road safely. 

Your liver plays a significant role in dealing with the alcohol in your system, converting it into water and carbon monoxide. At best, your liver can do this for one unit of alcohol an hour.

So, in theory, after consuming two units of alcohol in a pint of 3.8% ABV lager, you’d need to wait at least 2 hours before driving to be safe

How long after drinking am I safe to drive?

The truth is that even the morning after a night of heavy drinking, you are likely to have a high concentration of alcohol in your bloodstream if you’re heading off to work at 7am.

According to drink driving charity Brake.org, you should allow one hour as a baseline for alcohol to absorb and one additional hour for every alcohol unit consumed. 

If you happen to have enjoyed a 750 ml bottle of wine, you would need to wait at least 9 to 10 hours before hitting the road. But considering there’s no one-size-fits-all approach to knowing exactly how long your body takes to get rid of the alcohol, it may be safer to wait a little longer.

What is the alcohol limit for driving in the UK?

Knowing how many units of alcohol you’ve consumed is a good start. Still, it’s important to note that the standardised legal drink drive limits relate to the alcohol concentration in your blood, breath or urine. And as we’ve discussed, this alcohol concentration level can be made worse by factors outside your control, like age, weight and sex.

What is the drink drive limit in England, Wales and Northern Ireland?

According to gov.uk,

  • 35 micrograms of alcohol per 100 ml of breath
  • 80 milligrams (mg) of alcohol per 100 ml of blood
  • 107 mg of alcohol per 100 ml of urine

What is the drink drive limit in Scotland?

The drink-drive limits in Scotland are slightly lower than in the rest of the UK,

  • 22 micrograms of alcohol per 100 ml of breath
  • 50 milligrams (mg) of alcohol per 100 ml of blood
  • 67 mg of alcohol per 100 ml of urine

Why is the drink-drive limit not zero?

When looking at the numbers and how difficult it is to predict how much alcohol there may be in your system, you may wonder why the drink-drive limit is not simply zero. 

The answer is that everybody processes alcohol differently. You could still have traces of alcohol left in your system even though it has been some time since you last had a drink. In addition, the alcohol in everyday items like mouthwash and some cough mixtures, for example, may show up in testing. 

The current limits mean that police can differentiate between those with alcohol residue in their systems and those who may be impaired while driving as a result of drinking.

What are the drunk driving penalties in the UK?

Drink driving is a criminal offence, which can carry hefty penalties. 

Drink-driving cases are heard in criminal court. And if you’re found to be driving over the legal limit or unfit to drive through drink, you could face jail time, a criminal record, penalty points, an unlimited fine and a driving ban.

According to gov.uk, aside from criminal prosecution, a drink-driving conviction also means that:

  • It’s likely your car insurance costs will increase substantially.
  • It could impact your employment if you drive for work, as your employer will see the conviction listed on your licence.
  • It may make travel to countries like the USA more difficult.

In summary

It’s no secret that alcohol dulls reaction times and cognitive ability, so not driving if you plan to drink is always the best practice. 

The existence of drunk driving limits might suggest that there’s a certain amount of alcohol you can drink and still safely and legally drive. The truth is there is no catch-all here. 

If you’re drinking on a night out, consider a designated driver, a sober pickup, a licensed taxi service or public transport and be sure to get home safely!