# How long does it take alcohol to leave the system?



## Sylvester3 (15 Sep 2009)

*Re: Breathalysed and over limit next day*

_copied from another thread_

A good rule of thumb is to allow one hour per unit of alcohol - counting from when you finish your last drink. So if you have a pint then you will be clear 2 hours after you drink it, etc etc. I've used this rule since I learnt it at Uni back when I was 18 - it means you have to cadge a lift/get a taxi in the morning sometimes, but at least you aren't putting yourself or others at risk.

BTW, having a cooked meal would have no impact on existing blood alcohol levels. Only time can do anything about that.


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## mathepac (15 Sep 2009)

*Re: Breathalysed and over limit next day*

_ copied from another thread_

There is a rule of thumb that says a normal healthy adult, who is well rested, well nourished, emotionally stable, not on any medication, with a normal body-fat content, who is not dehydrated, has not imbibed alcohol the previous day, has a normally functioning liver and kidneys, drinking at a normal pace, etc, etc. has the ability to metabolise a single unit of beverage alcohol per hour on a given day (the hour starts when the last of the drink is taken). On a different day with any of the variables changed, that ability may change, upwards or downwards.

Gulping a two-unit drink and waiting two hours may not work; the liver has to work that bit harder to metabolise the additional beverage alcohol, so two hours may not be enough to do the job. As the effects on the liver tend to be cumulative, both short and long term, after three such drinks the metabolic efficiency of the liver is any one's guess.

Anyone acting on such ill-founded advice is behaving irresponsibly.


Sylvester3 said:


> ...   A 10 drink bender (which I've never had) would mean you shouldn't drive the next day at all. I've never considered that to be idiotic advice.


Very sensible - whether a "10 drink bender" consists of 10,15, 20 or more units units of alcohol, it ties in with the adage "If you drink, don't drive".

Even if all of the metabolites that indicate the presence and level of alcohol in a person's blood-stream and therefore brain have gone, post-bender, there are other issues to be considered such as :


Level of tiredness
Dehydration
Ability to concentrate
Emotional state (anxiety, worry, regret, anger, etc.)
Physical state (sweats, shakes, headache, dodgy tummy, etc.)
all of which may effect a person's ability to drive, cycle, roller-skate or maybe even walk safely.


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## Brendan Burgess (15 Sep 2009)

In this post, Linda O was done for drunken driving the next day



> I was stopped for regular check an a Garda breathilised me, i'm now being done for drunk driving! I know it sounds bad, I was stoped 6pm the next day and I was 35.5ml, so I was .5 over!!





> yea was a good night alright, wedding



I would be a bit wary the morning after a heavy night, but I would have assumed that I was completely clear by 6pm. 

I had a rough idea that it takes two hours to process a pint. So if I drank 10 pints up to 2 am, it would take 20 hours to clear the alcohol out of my blood. So if I had begun drinking at 6 pm, I would be alcohol free by 2 pm the next day? 

My maximum intake these days is about 6 pints, so I would expect to be clear about 8 hours later, assuming it takes me about 4 hours to drink 6 pints. 

Brendan


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## mathepac (15 Sep 2009)

This thread is on an identical topic, but either could stray into medical territory easily - http://www.askaboutmoney.com/showthread.php?t=121983


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## Caveat (15 Sep 2009)

Don't let _mathepac_ hear you talking like that Brendan! 

(Check out Liaconn's thread in LOS)

_Crossed with mathepac - naturally._


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## MANTO (15 Sep 2009)

Hi Brendan,

There are a number of factors that contribute to alcohol leaving the system, i.e. Gender, Metabolism, Age, Size etc.. so its hard to pin point the exact amount..



*Blood alcohol content* or *blood alcohol concentration* (abbreviated *BAC*) is the concentration of alcohol in a person's blood. BAC is most commonly used as a metric of intoxication for legal or medical purposes. It is usually measured in terms of mass per volume, but can also be measured in terms of mass per mass. Blood alcohol concentration is given in many different units and notations, but they are all relatively synonymous with each other numerically.
The number of drinks consumed is a poor measure of BAC, largely because of variations in weight, sex, and body fat. However, it is generally accepted that the consumption from sober of one standard drink of alcohol (e.g. 14 grams (17.74 ml) ethanol content by U.S. standard) will increase the average person's BAC roughly 0.02% to 0.05% and would return to 0% about 1.5 to 3 hours later (at a dissipation rate of around 0.015% per hour).


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## Ann1 (15 Sep 2009)

I think the state of one's liver also has a lot to do with it. Someone who drinks on a regular basis over many years might find it takes longer for their liver to process the alcohol.?


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## mathepac (15 Sep 2009)

mathepac said:


> ...  but either could stray into medical territory easily ...





Ann1 said:


> I think the state of one's liver also has a lot to do with it...


 That didn't take long, did it?


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## Ann1 (15 Sep 2009)

mathepac said:


> That didn't take long, did it?


 
No.... but still just slightly less time than it would take for 1 unit of alcohol to leave the system.


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## Brendan Burgess (15 Sep 2009)

I think that the Letting Off Steam thread is about whether the system is fair or not. I don't really want to get involved in that discussion.

I am not particularly interested in that issue, but I genuinely want to know if I have 5 pints between 10pm and 2pm on a Saturday night, what time is it safe to drive? 

The purpose of the ban on medical issues is to stop people seeking medical advice when they should be going to see their doctor. So I hope this doesn't break the rule. One of the mods will surely close it if they think it breaks the guidelines.


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## mathepac (15 Sep 2009)

There is no definitive answer Brendan, or more accurately there are several  answers, each of which maybe  correct for any one of us on a particular day, which is what I was trying to point out in post # 26 in this thread http://www.askaboutmoney.com/showthread.php?t=121983

It is a complex area that does not lend itself to simple one-line answers.

_ Mathepac - I have copied that useful post into this thread_


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## d2x2 (15 Sep 2009)

You could  to find out.


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## Brendan Burgess (15 Sep 2009)

> The number of drinks consumed is a poor measure of BAC, largely because of variations in weight, sex, and body fat. However, it is generally accepted that the consumption from sober of one standard drink of alcohol (e.g. 14 grams (17.74 ml) ethanol content by U.S. standard) will increase the average person's BAC roughly 0.02% to 0.05% and would return to 0% about 1.5 to 3 hours later (at a dissipation rate of around 0.015% per hour).



Manto 

Thanks for the link, but these guys do not make it easy to work out.

So it takes between 3 and 6 hours to get rid of one pint. 

That is a lot higher than the 2 hours I was working on.

Brendan


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## Brendan Burgess (15 Sep 2009)

mathepac said:


> which is what I was trying to point out in post # 26 in this thread http://www.askaboutmoney.com/showthread.php?t=121983



To quote a particular post instead of a thread

Right click on the number 26
Copy Link location
Paste it into where you want it

http://www.askaboutmoney.com/showpost.php?p=931219&postcount=26

Brendan


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## Brendan Burgess (15 Sep 2009)

I think I will buy one of those breath analysers in the chemists.

Brendan


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## sparkeee (15 Sep 2009)

i knew a professional boxer,he would very rarely take a drink and told me it would take weeks for him to work it out of his system,he was super fit the rest of us probably arent and dont notice it so much.


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## Ann1 (15 Sep 2009)

A friend of mine has to take monthly drug tests because of her job and she always leaves a minimum of 48 hours or 2 days.  Last time we were out she would not join us for a chinese meal after a having a few drinks as she said fatty foods slowed down the time it took the alcohol to leave her system. Females have a higher body fat content than men so that is also a factor.


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## John Rambo (15 Sep 2009)

I believe there are a number of factors - size, sex, full/empty stomach, physical fitness, general health, fatigue, metabolism etc. For example, I was breathlysed en route to play golf at approximately 10.30am after what was a pretty monumental session. If I'm brutally honest, I thought I was goosed but the reading was zero (meaning the 1 unit per hour "rule" hadn't applied). I think the hour per unit which seems to be conventional wisdom is conservative (i.e. many people absorb alcohol quicker but hardly anyone takes longer than this). Of course, the only way to be sure is not take any risks at all.


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## Pique318 (16 Sep 2009)

Brendan said:


> I think I will buy one of those breath analysers in the chemists.
> 
> Brendan


Ditto. €100 or so and you're secure in the knowledge that you're 'safe' (ish).



Ann1 said:


> A friend of mine has to take monthly drug tests because of her job and she always leaves a minimum of 48 hours or 2 days.  Last time we were out she would not join us for a chinese meal after a having a few drinks as she said fatty foods slowed down the time it took the alcohol to leave her system. Females have a higher body fat content than men so that is also a factor.


 Is alcohol a problem in a drug test ? It's still legal to drink in Ireland, right ??



John Rambo said:


> I believe there are a number of factors - size, sex, full/empty stomach, physical fitness, general health, fatigue, metabolism etc. For example, I was breathlysed en route to play golf at approximately 10.30am after what was a pretty monumental session. If I'm brutally honest, I thought I was goosed but the reading was zero (meaning the 1 unit per hour "rule" hadn't applied). I think the hour per unit which seems to be conventional wisdom is conservative (i.e. many people absorb alcohol quicker but hardly anyone takes longer than this). Of course, the only way to be sure is not take any risks at all.



I was breathalysed for the first and only time in my entire driving life (approx 14 years) about a year ago. I hadn't consumed an alcoholic beverage, nor cough mixture, nor cough sweets, nor sherry trifle etc.etc.. in about 3 days. I blew a 0.1 ! I drove away without thinking to ask the Guard when the thing was calibrated. Now I know the intoxilyser in the Garda Station is the next step but still. I was a bit surprised, tbh.


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## sparkeee (16 Sep 2009)

i would imagine everyone has some small amount of alcohol in their system even teetotallers,fruit or veg will ferment in the stomach.


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## Caveat (16 Sep 2009)

sparkeee said:


> ... told me it would take weeks for him to work it out of his system...


 
This doesn't sound believable to me.  

A bit like the old 'Bruce Lee's body was so fit and pure that it was an aspirin that killed him'


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## mathepac (16 Sep 2009)

sparkeee said:


> i would imagine everyone has some small amount of alcohol in their system ...


It would generally be very small. There may be rare instances where breathalyser detectable levels of ethyl alcohol are generated by the body, so-called auto-brew syndrome, but these are very rare and studies (Japan and the US that I am aware of) indicate common traits amongst the individuals where this happens -  

they are middle-aged
with gastrointestinal problems which have
had surgery and
have developed a yeast infection of some kind.

In general, normal healthy people don't ferment sugars to ethyl alcohol in readily detectable quantities. As soon as the presence of alcohol is detected our bodies begin to metabolise it in our stomachs and livers with an enzyme which triggers a  process that goes -

Alcohol -> acetaldehyde -> acetic acid -> water & carbon dioxide


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## olddog (16 Sep 2009)

sparkeee said:


> i would imagine everyone has some small amount of alcohol in their system even teetotallers,fruit or veg will ferment in the stomach.



Yes, that is true

Detecting very low levels of alcohol in the system is a vexed matter with Aircraft pilots

There are many threads on www.pprune.org on the topic

For example 

http://www.pprune.org/questions/304404-alcohol-limit-pilots.html


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## dewdrop (17 Sep 2009)

Maybe in the interests of healt there should be some comment about the damage that can be done when alcohol leaves the system.  I am a regular pint man myself!


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