How Long After Smoking Cannabis Can You Drive in Ireland

Cannabis & Driving in Ireland: How Long Before You’re Legally Safe?

Q: How long after smoking cannabis can I legally drive in Ireland?

A: That’s the wrong question — because there’s no clear answer.

And that’s what makes cannabis one of the riskiest drugs when it comes to Irish driving law.

Is there a legal limit for cannabis in Ireland?

Yes. The legal threshold for cannabis (THC) is 1 nanogram per millilitre of blood. That’s not a typo, it’s one billionth of a gram.

A trace amount. And it can stay in your system long after the effects have faded.

Weeks in fact.

So even if you feel completely sober — the Garda can still charge you.

And if the lab result from the Medical Bureau of Road Safety comes back over that limit, a driving ban is automatic if you’re convicted.

So how long should I wait after smoking cannabis?

No one can say for sure. And here’s why:

• THC is fat-soluble, which means it stores in your body and releases slowly

• It can be detectable for hours, days or even weeks depending on dose, frequency, metabolism and body type

• The MBRS doesn't give a safe timeframe, because there isn't one that applies to everyone

"The legal threshold for cannabis (THC)

is 1 nanogram per millilitre of blood.

That’s not a typo,

it’s one billionth of a gram"

If you smoke occasionally, it might be gone in 12–24 hours.

Might.

If you’re a regular user, it could take days.

Even if you smoke occasionally it could still take days.

Science does not apply here.

“A half-life of 1 hr means that 50% of the drug will be broken down in 1 hr, 75% at 2 hrs and so on.”— Medical Bureau of Road Safety FAQ

Sounds scientific. But for cannabis, the half-life is unpredictable.

So there’s no standard “safe window.”

Is it illegal to drive while high on weed?

Yes.

But even if you’re not high, if the MBRS finds you over the legal limit, you can be charged. You don’t need to crash.

You don’t need to seem impaired.

The number is enough.

"I know nothing about the law on conveyancing or probate,

because I don’t practice those areas.

If you came to me looking for advice in these areas

I’d refer you to a different lawyer.  

Think about that"

Bottom line: Don’t guess. Don’t rely on the internet.

Cannabis is different from alcohol. The law is stricter. There is no science here.

And once you’re charged, you’re in full defensive mode.

If you’re caught over the limit:

• You face a potential criminal conviction

• A mandatory disqualification (even for first-time users)

• Massive insurance hikes

• And possible visa or travel issues

Final Takeaway

So if you’re even asking how long to wait, it probably means you shouldn’t be driving yet.

Get proper legal advice.

And remember: solicitors are not all the same.

I know nothing about the law on conveyancing or probate, because I don’t practice those areas.

If you came to me looking for advice in these areas I’d refer you to a different lawyer.  

Think about that.

After all, it’s the choice between going off the road… or driving home.

And everybody wants to drive home.