How long does alcohol stay in your system?

Liz Wood AlphaBiolabs

By Liz Wood, Health Testing Specialist at at AlphaBiolabs
Last reviewed: 17/11/2023

In this article we discuss what happens to your body when you drink alcohol, how long alcohol stays in your system, and how alcohol abuse can affect your health.

What does alcohol do to you?

When we talk about the alcohol that we drink, we are talking about ethanol. Ethanol is a small molecule and is able to pass the blood-brain barrier, exerting its effects on both our mental and physical behaviours. 

Drinking alcohol can make us feel calmer and more relaxed at first. However, the more you drink, the more alcohol affects your brain, and you might start to slur your words, or find movement and coordination more difficult. In extreme cases, excessive drinking can cause you to become unconscious, and some alcohol overdoses can result in death.

How is alcohol metabolised?

Most of the alcohol we drink is metabolised (processed) by alcohol dehydrogenases. Alcohol dehydrogenases are enzymes which turn the alcohol (ethanol) into less active metabolites and then eventually into carbon dioxide and water. 

The more alcohol dehydrogenase enzymes we have, the more efficient the metabolism of alcohol. Those who have less alcohol dehydrogenases are more likely to suffer the effects of alcohol consumption (problems with coordination, slurred speech etc), because they have more alcohol circulating in the blood. 

Almost all of the alcohol we drink is broken down in the liver. The remaining unchanged alcohol (about 5%) is eliminated from the body through our sweat, breath and urine.

How does alcohol affect the brain?

Alcohol interacts with many different neurotransmitters and receptors in the brain. A neurotransmitter is like a messenger – it sends chemical ‘messages’ from a nerve cell (neuron) to another cell. A receptor is something that ‘receives’ the information from a chemical messenger. 

Two neurotransmitters affected by alcohol are GABA (gamma-aminobutyric acid) and dopamine. 

GABA is inhibitory – it stops or slows down the transmission of information. Alcohol can interact with GABA receptors, which leads to feelings of calmness and reduced stress or anxiety. 

However, when you drink alcohol excessively and chronically, your brain reduces the number of GABA receptors. This reduces the ‘calming’ effect of both the natural neurotransmitter GABA as well as alcohol on the brain. If someone is addicted to alcohol and they stop drinking suddenly, they can become anxious, agitated and experience sweating and tremors. Epileptic fits can also occur which are serious and can be dangerous. 

Dopamine is involved in the mesolimbic (reward) system. The reward system is where the brain associates activities, events, or some substances with a good, positive, or desirable outcome.

When we have a ‘rewarding’ experience, dopamine is released. This makes us feel good, and also motivates us to repeat the rewarding behaviour. When we drink alcohol and feel good, dopamine is released almost immediately, and our brain tells us to drink more, so that we continue to experience this rewarding effect. 

However, since alcohol doesn’t prevent the reuptake of dopamine, your brain responds by producing less of it. Your reward system motivates you to drink more, and the more you drink, the less dopamine your brain produces, continuing the cycle. 

People who are addicted to alcohol deplete their natural dopamine supply and rely on the consumption of alcohol to produce dopamine. When they don’t drink alcohol, they can begin to experience withdrawal symptoms and their mood may be negatively affected.

How does alcohol affect the body?

Alcohol affects the body in many ways because it affects many different bodily functions. 

Alcohol inhibits something called vasopressin – a hormone involved in the regulation of water secretion. When vasopressin is inhibited, your kidneys don’t know that they should be reabsorbing water. This results in rapid bladder filling and more frequent trips to the toilet!

The loss of water through vasopressin inhibition also contributes to a hangover the next morning. Excess drinking means you lose more water through urine which causes dehydration. This causes the dreaded hangover headaches, dry mouth and excess thirst. 

You might feel drowsy when you’ve had a few drinks (thanks to the interaction of alcohol on GABA receptors), but you will likely have a more disturbed sleep, leaving you feeling fatigued the next day.

Drinking alcohol also causes your stomach to produce more stomach acid, and delays stomach emptying. The excess stomach acid irritates your stomach lining, which can cause stomach pain, nausea and vomiting. It also increases your risk of getting peptic ulcers.

Drinking too much, even on just one occasion, can cause problems with the heart, liver or pancreas. Regular or chronic alcohol drinkers are also more susceptible to some cancers, and their immune system may also become compromised, leading to infection and disease.

How long does alcohol stay in your system?

The time that alcohol stays in your system depends on how well your body can metabolise it. Biological sex, age, body size, medications and health conditions all impact how long alcohol will stay in your system. 

There are a number of different tests that can be used to detect alcohol in the body, and each one has a different window of detection. 

How long does alcohol stay in your blood?

On average, alcohol remains detectable in your blood for about 24 hours. A blood alcohol content (BAC) test measures the amount of alcohol in the blood, and the result is usually shown as the amount of alcohol per given volume of blood. For example, if a BAC result is 0.05, there is 0.05 g of alcohol per 100 mL of blood. A BAC of 0.1 g per 100 mL (0.1%) is considered impaired, and 0.40% is potentially fatal. 

However, there are other blood tests on the market that can tell you whether alcohol has been consumed over a longer period of time. At AlphaBiolabs, we offer PEth, CDT, MCV and LFT tests, which can determine if a person is drinking excessively over an extended period of time by looking at specific biomarkers that indicate alcohol consumption or abuse. 

  • PEth (Phosphatidylethanol)

PEth is the most accurate blood alcohol test. PEth is a direct marker of alcohol, so is only detected if alcohol has been consumed. It can distinguish between those who drink alcohol chronically and those who drink on occasion. It can provide an overview of alcohol consumption of up to four weeks.

  • CDT (Carbohydrate deficient transferrin)

CDT is a protein that is mainly made in the liver. People who drink excessively have higher amounts of CDT in their blood, but people who don’t drink or drink moderately will have low CDT levels. CDT is a measure of chronic alcohol consumption. 

  • MCV (Mean corpuscular volume)

The MCV test is a measure of the size of the red blood cells. People who drink heavily for a long period of time have abnormally large red blood cells because their alcohol consumption has damaged the bone marrow. 

  • LFT (Liver function test)

LFT looks for enzymes in the blood that are produced by the liver. Excess alcohol consumption can damage the liver, decreasing its function. The amount of these enzymes available can indicate whether there are problems with the liver. 

If you want to find out more about our alcohol blood tests, you can visit our alcohol testing page here

How long does alcohol stay in your urine?

Depending on the urine testing kit being used, alcohol can be detectable in urine from 12 hours to 4 days. More advanced urine testing kits are able to detect alcohol for around 4 days, usually because they are more sensitive. 

How long does alcohol stay in your breath?

The amount of time alcohol stays in your breath depends on both the person drinking and the amount they drink. As mentioned above, alcohol can stay in your system for varying amounts of time depending on multiple factors, such as sex, body size and pre-existing health conditions. 

On average, alcohol can be detected 12-24 hours after consumption. Alcohol can be measured using a device called a breathalyser. Any alcohol in the breath causes a reaction in the breathalyser, which in turn creates an electrical current. The electrical current produced is proportional to the amount of alcohol vapour present – the more alcohol in a person’s breath, the stronger the electrical current and therefore the higher the blood alcohol content (BAC).

How long does alcohol stay in your saliva?

Alcohol may be present in the saliva for around 10-24 hours in trace amounts. Saliva can be tested for the presence of alcohol using a swab. The swab collects saliva from the inside of your mouth. Any alcohol present in the saliva sample is then detected using a chemical assay test strip. Alternatively, samples can be sent away to a laboratory where they will be tested for the presence of alcohol. 

How long does alcohol stay in your hair?

Alcohol is detectable in hair for up to 12 months. 

At AlphaBiolabs, we can look for two different alcohol markers, ethyl glucuronide (EtG) and fatty acid ethyl esters (FAEE). 

EtG is produced when alcohol is consumed. It is a metabolite of ethanol and is formed in the liver upon consumption. EtG is mainly deposited into the hair through sweat. 

FAEEs are also metabolites of ethanol. They are formed in almost all tissues in the body after you consume alcohol. FAEE gets into the hair strands through sebum.

Alcohol can be detected in body hair as well as head hair. However, only EtG should be tested for body hair samples, as FAEE is incorporated into the hair differently to EtG. 

Both EtG and FAEE testing have strengths and weaknesses in their ability to detect excess alcohol consumption. You can read more about EtG and FAEE testing at AlphaBiolabs in our hair alcohol testing page

Elevated levels of FAEE and EtG are indicative of excess alcohol consumption. If EtG and FAEE hair analysis is paired with alcohol blood tests, such as PEth, you can obtain a more accurate and detailed picture of a person’s drinking habits in a given time frame.

What factors can affect how long alcohol stays in your system?

There are a variety of factors that can affect how long it takes for alcohol to leave your system. Age, body size, medications and health conditions can all play a role in how slowly or quickly alcohol is metabolised. Here, we look at some of the different factors in more detail. 


The reason for the impact of age on alcohol metabolism is multifaceted. 

Generally, as we age, we lose muscle mass and gain fat. Only a very small amount of alcohol enters fat tissue, so people with a larger fat tissue percentage will usually have higher blood and tissue concentrations of alcohol compared to someone with a lower body fat percentage. The same effect is seen in women, who have more subcutaneous fat than men. In short, it can take longer for the body to metabolise and eliminate the alcohol from our bodies. 

We also lose water volume in our bodies as we get older, which further contributes to higher blood alcohol content. 

Aging also increases our chances of developing a health condition. Drinking alcohol, especially in excess, can exacerbate both physical and mental health conditions. Some of these conditions may impact the time it takes for the body to fully eliminate alcohol. 


Alcohol affects you differently depending on your biological sex. 

In general, men have a lower body fat percentage and higher muscle mass compared to woman. Higher subcutaneous fat means that more alcohol stays in your body and for stays for longer. 

Women generally have more fat and less muscle than men. They also usually have a smaller blood volume. This means that when a woman drinks the same amount of alcohol as a man, even if weight has been adjusted for, their BAC will be higher. 

Some women may have lower levels of the alcohol dehydrogenase enzymes. These enzymes break down almost all of the ethanol into its metabolites, which can then be eliminated from the body (e.g. through urine). If you have lower levels of alcohol dehydrogenases, then you can ‘overwhelm’ the enzymes quicker, which means you have more alcohol circulating your blood. You might feel the intoxicating effects of alcohol more rapidly, and it will also take your body longer to clear the remaining alcohol from your system. 

Food and water

Drinking on an empty stomach really does impact how rapidly alcohol enters your bloodstream, as well as how long the effects last. 

Consuming alcohol on a full stomach slows the absorption of alcohol into the blood. This means it takes longer for BAC to reach peak levels compared to drinking alcohol on an empty stomach, and may even lower the peak BAC. 

However, whilst eating a good meal before drinking alcohol might lower your blood alcohol content, it won’t make the alcohol leave your system any faster. 

Drinking water and ensuring you stay hydrated can also help to lower your BAC. It reduces the amount of blood and increases the water volume in muscles, resulting in a lower BAC.

However, it does not help you to ‘flush’ the alcohol out of your system any quicker. 

Despite this, drinking water, particularly if also consuming alcohol, is important to keep yourself hydrated. We lose lots of water when drinking alcohol because alcohol is a diuretic. Dehydration contributes to some of the nasty hangover symptoms you might experience, so drinking plenty of water will not only lower your BAC, but it might make you feel a bit better too. 


Some medications can affect how alcohol is processed in the body. Medications can also interact with alcohol, even if they’re not taken at the same time. 

Some medicines may impact your blood alcohol content or the time it takes for your body to process alcohol, meaning that they can impact the time it takes for alcohol to leave your system. 

Medications can also cause adverse and severe side-effects if taken with alcohol. The list of medications that can cause problems when consumed with alcohol is extensive. Numerous medications for ailments including, but not limited to, pain, diabetes, mood disorders, allergies, heart conditions, neurological conditions and high blood pressure can all cause problems with your health if taken with alcohol. 

It’s really important to consult your doctor if you are taking medication of any kind before consuming alcohol. The safest choice is to not drink any alcohol if you are on medication. 


When it comes to alcohol tolerance and alcohol dependency, there are a number of genetic factors involved.

Some research has suggested that alcohol use disorder can run in families and genes are responsible for half the risk (NIAAA, 2008). Environmental factors are also important in the risk of developing alcohol use disorder.

Some people have a gene variant that makes them susceptible to adverse effects of drinking, such as facial flushing, dizziness, and rapid heartbeat. Some individuals with this variant don’t like these effects and so might avoid drinking alcohol altogether. 

There are also some genetic variants that alter the amount of alcohol dehydrogenases in your body. This can impact the rate of alcohol metabolism and therefore how much alcohol is circulating in your blood. 

Type and amount of alcohol consumed

Different drinks have different amounts of alcohol in them. You can find out how much alcohol is in your drink by looking for the ABV % on the bottle or can. A bartender should also be able to tell you how strong your drink is. 

A standard drink contains 10 grams of pure alcohol. This equates to:

  • One small glass of wine (12.5% volume)
  • One half pint of regular strength beer
  • One standard measure (35ml) of spirits
  • One regular bottle of alcopops

In short, it’s about the type of drink and how much you drink. Drinking too much of any alcoholic beverage puts you at risk of intoxication and associated health problems, and also prolongs how long the alcohol will stay in your body. 

For more information about the amount of alcohol in different beverages, you can visit the Drinkaware website.

Can you sober up faster by drinking water or coffee?

Contrary to popular belief, drinking coffee or chugging water will not sober you up. In fact, there is nothing you can do to make alcohol leave your system any quicker!

Drinking coffee or water might help you feel more alert. They may even appear to alleviate some symptoms of alcohol intoxication. 

However, the only thing that can make the alcohol leave your bloodstream is time. Your body processes alcohol by breaking it down using alcohol dehydrogenase enzymes. 

Drinking water or coffee, eating fast food or a salad, taking a cold shower or going on a run does not have any effect on how quickly these enzymes can break alcohol down.

Drinking water helps to replace some of the water lost during alcohol consumption, decreasing your chances of becoming dehydrated. Ensuring you stay hydrated can help reduce the severity or likelihood of you getting a headache or dry mouth, but it won’t speed up how quickly your body can get rid of the alcohol.  

The safest way to avoid prolonged alcohol intoxication is to not drink at all, or to drink alcohol in moderation. Being under the influence of alcohol can impact many activities, like driving a car or operating machinery, so it’s important to avoid drinking too much, and ensuring you wait long enough after drinking before doing any activity that could be affected by alcohol consumption.

What are the risks of alcohol abuse?

There are many risks involved when alcohol is abused. In this section, we explore what these risks are and how they can impact your life. 

Short-term health risks

Short-term risks describe the often immediate effects of excessive drinking. They can be experienced by those who binge drink on occasion, or people who are chronic drinkers. Risks include:

  • Alcohol poisoning
  • Injuries and accidents
  • Physical and/or sexual violence 
  • Anti-social behaviour
  • Risky sexual behaviour

Alcohol poisoning happens when the alcohol in the body interferes with bodily functions, such as breathing, heart rate and gag reflex. Alcohol poisoning can be extremely dangerous – it can cause someone to become unconscious, fall into a coma, or can even cause death. 

You are more at risk of having an accident, such as a fall or car crash, if you are under the influence of alcohol.

Aside from causing accidents and injuries, driving whilst under the influence of alcohol can land you with a criminal record, a driving ban, an unlimited fine, or up to six months in prison. This can impact your relationships with family, friends and partners, and can affect your ability to keep or get a job. Causing death under the influence of alcohol can result in a life sentence.

Physical and/or sexual violence can also occur when under the influence of alcohol. This is because alcohol affects our decision-making and self-control (Alcohol Action). Drinking too much can also lead to anti-social behaviour. Anti-social behaviour can be intimidating to those around you, and can also lead to aggression, violence and criminal damage. 

Being under the influence of alcohol may also cause us to lose our inhibitions and partake in risky behaviours that we would normally avoid or take precautions with when sober. This can include engaging in risky sexual behaviour, like having sex without protection, or with multiple partners. This increases your risk of contracting an STI or having an unplanned pregnancy. Alcohol weakens your immune system, meaning it is easier to catch infectious diseases. People who are dependent on alcohol can also find it very hard to fight off infections.

Limiting the amount you drink, or not drinking at all, reduces the chances of you engaging in behaviours that put you at risk of injury, violence or infection. 

Long-term health risks

Long-term health risks are the risks to your health because of prolonged, excessive drinking. These risks don’t just go away the morning after – they are serious risks that can shorten your life expectancy and reduce your quality of life. Some of these risks include:

  • Liver disease 
  • High blood pressure
  • Stroke
  • Various cancers (e.g. liver, mouth, breast, bowel, head and neck)
  • Pancreatitis
  • Dementia
  • Depression

Alcohol-related liver disease (ARLD) happens when you drink too much for a long period of time and cause damage to your liver. Your liver is usually very good at regenerating, but those who drink excessively and/or chronically are at risk of causing permanent damage to their liver. There are three stages to ARLD: the alcoholic fatty liver and alcoholic hepatitis are the first two stages and can be reversible if alcohol consumption is stopped. The third stage is alcohol-related cirrhosis. Cirrhosis is not typically reversible and can severely shorten your life expectancy if you don’t stop drinking alcohol. It’s also associated with other complications like kidney disease. 

Alcohol can also increase your blood pressure. This is due to several reasons, including the calorie content of the alcoholic drink itself. High blood pressure, or hypertension, increases your risk of cardiovascular disease. This in turn increases your risk of having a heart attack or a stroke. 

Drinking alcohol also increases your risk for several different types of cancer, including breast, bowel, mouth, throat and liver cancer. Alcohol causes cancer through various means, such as direct damage to cells, changes in hormone levels, and changes in cells of the mouth and throat. People with cirrhosis are also more likely to get liver cancer. 

Excess alcohol consumption can cause pancreatitis. The pancreas produces enzymes that break down food and hormones such as insulin. Pancreatitis is when the pancreas becomes inflamed and therefore the pancreas isn’t able to produce the enzymes and hormones properly, causing serious illness. 

Regular drinking over a long time causes damage to the brain, which can lead to alcohol-related dementia or brain damage (ARBD). ARBD can affect your mood or ability to complete tasks like getting dressed or cooking a meal. It can also cause memory problems and difficulties interacting with other people (HSE). 

Prolonged alcohol exposure also affects your mood. Drinking in moderation can often help us feel relaxed, however for people who drink larger quantities of alcohol more frequently, the effects tend to wear off quickly. This causes chemical changes in your brain that affect your mood, giving rise to negative feelings like anxiety, depression and anger (Drinkaware).

Where can I get help for alcohol problems?

There are lots of ways you can get help if you think you have a problem with alcohol. Being open and honest about your drinking is important for getting you the right kind of help – healthcare providers and support groups won’t judge you, they are there to help.

You might want to start with your GP, who can advise you on which support groups may be most beneficial. They can also help you form a plan on how to cut down on your drinking. It’s especially important to seek proper medical advice if you are physically dependent on alcohol, because stopping overnight can cause serious harm. If you have symptoms of alcohol withdrawal, particularly if those symptoms are severe, you must immediately call 112 or 999. For more information on alcohol withdrawal and how to seek help, visit the HSE alcohol services page

Alcoholics Anonymous provides support meetings across Ireland.

Where can I get an alcohol test?

AlphaBiolabs is one of Ireland’s leading providers of laboratory alcohol testing services for members of the public, the legal sector, and the workplace sector.

Our accredited laboratory can test a variety of samples for the presence of alcohol and its metabolites, including breath, blood, hair, and nails.

We also offer alcohol monitoring in the form of SCRAM Continuous Alcohol Monitoring®.

To discuss your alcohol testing needs, call our Customer Services team on 01 402 9466 or email

Alcohol Testing Services

Explore our alcohol testing services.

Liz Wood AlphaBiolabs

Liz Wood

Health Testing Specialist at at AlphaBiolabs

Liz joined AlphaBiolabs in 2021, where she holds the role of Health Testing Specialist.

As well as overseeing a range of health tests, she is also the lead on several validation projects for the company’s latest health test offerings.

During her time at AlphaBiolabs, Liz has played an active role in the validation of the company’s Genetic Lactose Intolerance Test and Genetic Coeliac Disease Test.

An advocate for preventative healthcare, Liz’s main scientific interests centre around human disease and reproductive health. Her qualifications include a BSc in Biology and an MSc in Biology of Health and Disease.

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