Alcoholic drinks vary in strength. Beers contain about 5% alcohol, spirits like vodka usually contain about 35%. Wine is in between. Bottles and cans of alcohol should have information on how much alcohol they contain as a percentage.

Alcohol is a nervous system depressant, meaning it works by slowing down parts of the brain. Areas that it affects include those that control inhibition, thought, perception, attention, judgement, memory, sleep and coordination.

The effects of alcohol on behaviour depend on the level of alcohol in the blood:

Low blood-alcohol-concentration will depress parts of the brain involved in inhibition, making the user more animated and social. It may also lift your mood, but even at low levels alcohol can still affect coordination and judgement.
concentrations of alcohol will begin to seriously hamper coordination, memory and judgement. Alcohol also depresses the ability to regulate emotion, which is why intoxicated people can become emotional or aggressive.
enough concentrations of alcohol in the blood will cause users to become woozy and they may pass out. A potentially fatal concentration of alcohol in the blood will depress areas of the brain involved in breathing, causing breathing to slow dramatically and eventually stop.
also causes the user to urinate more, causing dehydration. Following heavy use of alcohol the user may experience a ‘hangover’, which typically is experienced the morning after (although a hangover can last longer). Effects of a hangover can include: nausea and vomiting, headache, thirst, sensitivity to light and noise, diarrhoea, low mood and anxiety. People can generally be described as not being at their best on a hangover, and studies have found things like memory to be worse during a hangover.

Alcohol in a social context often helps people to be happier and more confident. Tipsy people can be chatty and giggly, although some may become withdrawn. Alcohol often makes people say and do things they normally wouldn’t (reduces inhibitions). When people aren’t at bars, clubs and parties, many people consume alcohol for its calming effects, for example, wine with an evening meal. Many people say they enjoy alcoholic drinks for the taste, rather than using it as a drug. However, the taste of alcoholic drinks is usually unpleasant to people when they first try them and later enjoyment of the taste may be a learned association with the drug. After a couple of drinks, people start to lose the ability to concentrate and think straight.

Alcohol at high concentrations is quite toxic, which makes it useful for killing germs. Alcoholic hand gels and wipes are an essential means of preventing infection, and mouthwashes often use alcohol too. However, drinking alcohol doesn’t work to cure infectious diseases.

It has been suggested that alcohol in moderation could have some health benefits (see alcohol myths and misunderstandings below). However, any suggested health benefits are outweighed by the potential damage to your health.

Historically, alcohol was used to stupefy people before having painful operations such as getting their teeth pulled out. Ethanol has also been used as an antidote to poisoning by methanol, a more toxic alcohol chemical which causes blindness and death.

Alcohol impairs judgment and drunk people are more likely to be reckless and commit violent and sexual assaults. More than 40% of all intentionally caused injuries would not have occurred without alcohol. Additionally, serious injuries or deaths can result from the loss of judgment and coordination caused by alcohol. House fires (e.g. from drunken cooking attempts, or falling asleep whilst smoking), and car accidents (from drunk drivers or drunk pedestrians crossing the road) are often linked to alcohol intoxication.

If someone has passed out from drinking too much alcohol it is possible for them to choke on their own vomit. Large amounts of alcohol can also cause a person to fall into a coma-like state or stop breathing. The level of risk increases the more drunk you are, which means that the most important way to reduce your chance of being harmed is by drinking less. Many more harms are associated with long-term use of alcohol (see below).

Yes. Alcohol causes and worsens many health conditions, especially in large amounts. If you have high blood pressure, cardiovascular disease, liver conditions, conditions that make you bleed easily, mental health issues, or any other serious health problems, alcohol may cause you greater harm than it does the average person. You may benefit from discussing this with your doctor.

Drinking whilst pregnant can cause harm to the foetus, particularly drinking heavily in the early stages. There is no proof that the occasional small drink when pregnant is harmful, although there has not been enough research to rule this out.

Combining drugs usually increases the risks. As well as killing people on its own, a very significant proportion of deaths from drug poisoning are caused by alcohol taken in combination with other drugs.

Alcohol is a depressant and when taken with other drugs which have depressant properties the effect is multiplied. This makes it more likely for someone to pass out and choke on their own vomit or stop breathing. Drugs that can have this effect include the opiates, (such as heroin and methadone), benzodiazepines, (such as ‘Valium’ / diazepam or temazepam), and dissociatives (such as ketamine and DXM). A dose of these drugs which you have taken before without problems could be fatal in combination with alcohol.

Alcohol addiction and tobacco addiction are tightly associated, with high proportions of people dependent on one substance also being dependent on the other. Alcohol seems to make people enjoy smoking more, and a common trajectory of addiction is people progressing from only smoking when socialising and drinking to smoking all the time. The chance of mouth cancers is also much higher in people who smoke and drink together, compared to people who use one but not the other drug. Care should be taken not to chain-smoke when drinking.

Many medical drugs have side-effects when taken with alcohol. Others may not work effectively. Always read the leaflet or check with your doctor.

Alcohol dependence, often called alcoholism, is common. Dependence on alcohol means that the user has lost some or all control over their use of alcohol and are likely to suffer withdrawal effects if they don’t drink. This is more common in men, although women who are alcohol dependent usually suffer more severe harms as a result of alcoholism.

Not everyone who drinks alcohol is equally at risk of becoming dependent. Drinking from an early age and using alcohol as a tool to blot out stress and anxiety are just some factors associated with drinking too much and becoming dependent. Alcoholism can run in families, due to both genetic reasons and the influences people are exposed to. Traumatic experiences in early life, such as abuse, increase the chances of becoming alcohol dependent.

Being addicted to alcohol (alcoholism, alcohol dependence) makes people particularly vulnerable to the many health harms that alcohol can cause. Addiction changes a person’s priorities, which can be devastatingly disruptive to the lives and wellbeing of the addicted person and their families. People who are worried about alcohol addiction can get help and support by visiting their doctor.

People who are alcoholic find it very difficult to give up. Mildly addicted people suffer psychologically when they try quitting and may get cravings and feel anxious and miserable without drinking. Addicted drinkers become physically as well as psychologically reliant on alcohol. Physical reliance on alcohol means that a person’s body has adapted to having alcohol in it, and so removing the alcohol causes physical withdrawal symptoms. Quitting can cause flu-like or hangover-like withdrawal symptoms for about 3 days. Withdrawal from more severe alcoholism can have dangerous consequences, especially episodes of delirium tremens, which is potentially fatal. This includes shaking, hallucinations and a racing heart.

Withdrawal for severe alcohol addiction should only be attempted with medical help.

Health harms

Whether addicted or not, drinking large amounts of alcohol causes or increases the risk of diseases in almost all parts of the body, including the brain. The harms of drinking too much alcohol are often wrapped up with other health problems, such as a bad diet, and social problems such as poverty and unemployment. Alcohol causes damage to the heart, pancreas and other organs. The liver, which works to detoxify the body from alcohol, is often worst affected. The death toll from liver disease has been steadily rising over the last few decades, which can largely be put down to alcohol use.

Alcohol is also a carcinogen. It causes or increases the risk of many types of cancer including common ones like breast cancer, although moderate drinking seems to reduce the risk of a few rarer cancers. Alcohol can also cause diabetes, hormonal imbalances and sexual dysfunction.

Alcohol is particularly toxic to the brain. Women who drink heavily while they are pregnant may cause severe harm to the foetus, especially to the foetus’ developing brain. This is called foetal alcohol syndrome and in severe cases this causes profound intellectual disabilities and behavioural problems. In adults, alcoholism causes brain shrinkage and is the second biggest cause of dementia. Long-term alcoholism with malnourishment can cause Wernicke–Korsakoff syndrome, which can leave permanent brain damage with dementia and amnesia (inability to remember).

About a quarter of people with alcohol dependence suffer from mental illnesses. However, it is often difficult to tell whether some mental health conditions are caused by alcohol, or whether people drink to try to deal with their conditions. Sometimes both can be true, creating a vicious circle. For example, many people with alcohol dependence may be self-medicating for their anxiety and depression, which can in turn add to their condition.

Damage to employment, families and communities

An unhealthy relationship with alcohol can impact others aside from the drinker. All addictions can make it difficult to hold down a job, and can be damaging to relationships. It can be very hard to live with an alcoholic or binge drinker. Binge drinking is associated with anti-social behaviour that can fracture families and communities. Alcoholism like any addiction takes up time and resources, making it very difficult for homeless and vulnerably housed people to improve their situation. It can be a serious obstacle to employment and rehabilitation.

Association with crime and antisocial behaviour

When people are under the influence of alcohol, especially after binge drinking, they are often less able to control violent impulses or act with good judgement. The majority of assaults on young people which lead to hospital treatment are alcohol-related, and roughly half of domestic violence occurs after the perpetrator has been drinking. Alcohol is a major factor in the maltreatment of children. Drunkenness, even when non-violent, uses up police time, accounting for most arrests that occur at night. Very drunk offenders are particularly time-consuming, as they are more likely to be disruptive and uncooperative, and they need to be checked every few minutes to ensure their safety after arrest.

Being drunk also makes people more likely to be victims of crime. Whilst sexual assault can never be blamed on the victim and most rape victims are not drunk, in assaults which are facilitated by drugs alcohol is almost always present, and is often the only intoxicant involved.

Are you in control over how much you drink?

It is very important to be aware of and in control of what you are drinking. People who drink moderately are not immune from all the risks of the drug, but are far more likely to avoid serious harm. As a general rule of thumb, the less you drink, the better for your health. As everyone has different levels of tolerance to alcohol, as well as different speeds of processing alcohol, it is important to know your own limits. Sticking to the same drink might make it easier to judge how much you are drinking. Drinking spirits makes it easier to drink too much too quickly.

Do you know how you are getting home?

Alcohol inhibits the ability to drive safely. Some countries have a legal limit on the amount of alcohol allowed in the blood of someone driving, in other countries driving with any alcohol in the blood is illegal. Driving with a little under the limit is still more risky than driving with no alcohol in your system. On top of being more likely to hurt yourself or others, if you are found driving over the legal limit you can lose your driving licence, face a fine, lose your job, or even go to prison. There really is no reliable way to measure how much alcohol will affect you or put you over the limit as this depends on tolerance, body mass, gender, and how quickly you process alcohol.
groups choose a designated driver on nights out, who remains sober so they can drive others home.

Consider the risks the morning after

You can still be over the legal limit the next day after a heavy night of drinking. In fact, 10% of drunk drivers are caught between 6 and 12 the next morning. Additionally, you may still have poorer reaction times and ability to focus when hungover.

Drinking patterns

It’s not just the quantity of alcohol that is important, but the pattern of drinking. Someone who has one or two pints of beer every night may be harming themselves less than someone who drinks rarely on weekdays but binges most weekends.

How to look after someone who passes out from drinking

If someone has too much alcohol they may pass out. They could choke on their own vomit, which can happen when people are sick without being fully conscious. The first thing you should do is lay them on their side in the recovery position so that if they do throw up it is less likely to block their airway. Check on them regularly. You should call emergency services if they are unresponsive and cannot be woken, if they are throwing up without waking up, or if they have abnormally slow, shallow or irregular breathing. If you do need to call for help you should stay with them till emergency services arrive.

Does drinking water cancel out the effects of alcohol?

Drinking water or soft drinks will not protect your liver and other organs from the harm of processing alcohol. However, it may regulate your pace of alcohol consumption, which will make it less likely that you accidentally get much drunker than you intended. It also helps with the dehydration caused by alcohol which could help you feel better in the morning.

Is tolerance to alcohol a good thing?

Tolerance to alcohol is often thought of positively, and is associated with toughness. Although being tolerant to the effects of alcohol means that someone will get less drunk, it also makes them likely to drink larger amounts, making them more at risk of harms like liver disease and alcohol addiction. Tolerance to alcohol also runs in families, which is one of the reasons why alcohol addiction runs in families.

Does mixing drinks makes you more drunk?

Mixing drinks can make you feel sick or nauseous because it upsets your stomach and makes it easier to drink more than you think you are drinking. However, the drug in all types of alcoholic drinks is the same, so there is no known reason that mixing drinks would cause greater drug effects.

Does coffee sober you up?

Caffeine may make a drunk person less sleepy and more alert but it will not neutralise the alcohol in your system. Therefore drinking coffee to perk yourself up before doing something you would not do drunk (like driving) is a bad idea. Also using caffeine-containing energy drinks to keep you going so you can drink more or for longer just increases the total amount of alcohol your body has to deal with, as so increases the potential for harm.

Is alcohol in moderation good for you?

There is a common misconception that alcohol, ‘in moderation’, has proven health benefits. In fact, most of the total number of deaths and diseases caused by alcohol happen to people in the large majority of the population who are ‘moderate’ drinkers, not in the minority who are heavy drinkers. No-one should justify their alcohol consumption with the belief that they are benefiting their health.

There is some controversy and contested evidence about whether light drinking could be protective against specific conditions, like heart disease in middle age. A controlled trial, the only kind of study which could demonstrate this for certain, is impossible. Some observations at the population level (epidemiological research) seem to show that the middle-aged people who are the least likely to get and die from heart disease are not those who never drink, but those who drink a little. However, this does not prove that drinking a little makes you healthier than not drinking, as there could be other explanations for the findings. For example, some non-drinkers in the samples may never drink because they have health problems, or because they quit drinking after it harmed their health. An analysis of many studies found that the studies which showed that alcohol seemed most protective against heart disease were the ones that were worst at taking these other factors into consideration.

Even if light drinking can be protective against heart disease as some research suggests, the intake of alcohol which seems associated with the smallest chance of illness and death is very low, around half a pint of beer or half a glass of wine. Increased harm is observable at levels not much higher than this.

Also, there is convincing evidence that people routinely underestimate their alcohol use so people who think they drink safe or even beneficial amounts may actually be drinking at harmful levels.