Can I Have One Drink and Drive? Here’s What Most People Get Wrong

Can I Have One Drink and Drive in Ireland? | Drink Driving Law Explained

Can I Have One Drink and Drive? Here’s What Most People Get Wrong

It’s probably the most common question I get.

“Sure I only had one. I’d be under, wouldn’t I?”

And it’s asked with genuine confusion—often by someone sitting across from me after being arrested.

There’s a widespread belief that one drink is always safe.

That one pint or one glass of wine leaves you “just under” the limit.

Let’s have a look at why that belief can be dangerously wrong.

"According to the MBRS 2023 Annual Report,

the median blood alcohol level among drivers tested

was 153mg/100ml—

more than three times the legal limit for most drivers,

and over six times the limit for learner, novice, and professional drivers"

1. Ireland Has One of the Lowest Limits in Europe

In Ireland, all forensic testing of blood and urine for alcohol is carried out by the Medical Bureau of Road Safety (MBRS)—the State’s official laboratory for the testing of blood and urine specimens.

The legal blood alcohol limit is just 50 milligrams per 100ml of blood.

That’s one of the lowest limits in Europe.

It used to be 80mg, the same as the current UK threshold, but was lowered to presumably target road deaths.

So, the gap between one drink and being over the limit is much narrower than people think.

2. One Drink Can Push You Over—Depending on the Person

Here’s the problem with general advice like “You’ll be grand after one.”

• A pint of beer contains about 2 standard drinks.

• A large glass of wine is also 2 standard drinks.

• Even a single pub measure of spirits is one standard drink—which means one hour to leave your system.

But this assumes a lot:

• You’ve eaten.

• You’re not tired.

• You’re not dehydrated.

• You’re not on medication.

• You’re of average weight and metabolism.

The Medical Bureau of Road Safety makes it clear: blood alcohol levels vary wildly between individuals—even after the same drink.

So, while you might process that drink in an hour, someone else might take two.

"At the roadside this is a breath specimen.

This device only checks for alcohol on your breath,

not whether you are scientifically over the limit.

That test happens later in the station, after you’ve been arrested"

3. Feeling “Sober” Doesn’t Mean You’re Under the Limit

This is where most people get caught.

They feel fine. They don’t slur. They’re steady on their feet.

But they’re still over the legal limit.

Why?

Because alcohol impairs judgement before anything else. It tricks you into thinking you’re okay when you're not.

And in a courtroom, the only thing that matters is what’s in your blood, urine, or breath.

According to the MBRS 2023 Annual Report, the median blood alcohol level among drivers tested was 153mg/100ml—more than three times the legal limit for most drivers, and over six times the limit for learner, novice, and professional drivers.

That’s the average.

4. DrinkAware’s Calculator Is a Guideline—Not a Guarantee

Even drinkaware.ie the national alcohol awareness charity, warns that estimates about “safe” limits are unreliable.

Their calculator is based on idealised metabolism rates—but metabolism isn’t a science experiment. It’s a human body.

They state:

“The calculator is a guideline only and does not reflect how alcohol is processed in your body. Always leave a longer time if in doubt.”

So even if you’ve only had one drink, you could be over the limit for reasons entirely outside your control.

5. The Most Common Arrest Time Is Between 10pm and 4am

According to the MBRS, the most common time Gardaí collect blood or urine samples is between 10pm and 4am.

In 2021, 44% of all drink driving specimens were taken in that late-night window. That’s when people assume they’re fine after “just the one.”

In 2023, over 5,400 drivers were arrested and tested for alcohol. The vast majority didn’t believe they were over the limit at the time.

This isn’t about wild drinking sessions. It’s about misjudging what one drink, or one more drink can do.

6. Gardaí Don’t Need You to Look Drunk

This often surprises people.

Gardaí can request a test if they suspect impairment.

You don’t need to be falling over.

You just need to give them a reason to check.

At the roadside this is a breath specimen.

This device only checks for alcohol on your breath, not whether you are scientifically over the limit. That test happens later in the station, after you’ve been arrested.

So, it’s possible to fail to roadside breath test but pass the later breath test in the station.

But if you fail the test in the station, no matter how coherent or calm you appear—you’re over.

The law is absolute.

Final Word: It’s Not About How You Feel

If you’re asking, “Can I have one drink and drive?” you’re probably already taking a risk.

The law doesn’t test how drunk you feel. It tests what’s in your breath, blood or urine.

And because Ireland’s limit is so low, even one standard drink can put you at risk of being over—especially late at night, when the body is already under stress.

And if you are asking yourself that question, shouldn’t you be sceptical about your assessment of your sobriety?

After all, your choice might be the difference between going off the road or driving home.

And everybody wants to drive home.