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Alcohol ˈal-kə-ˌhȯl

By Patrick G. O’Connor, MD, MPH, Professor of Medicine; Chief, Section of General Internal Medicine, Yale University School of Medicine

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  • Genetics and personal characteristics may play a part in the development of alcohol use disorders.

  • Drinking too much alcohol may make people sleepy or aggressive, impair coordination and mental function, and interfere with work, family, and other activities.

  • Drinking too much alcohol for a long time can make people dependent on alcohol and damage the liver, brain, and heart.

  • Doctors may use questionnaires or determine the blood alcohol level to help identify people with an alcohol use disorder.

  • Immediate treatment may include assistance with breathing, fluids, thiamin, other vitamins, and, for withdrawal, benzodiazepines.

  • Detoxification and rehabilitation programs can help people with severe alcohol use disorders.

About 45 to 50% of adults currently drink alcohol, 20% are former drinkers, and 30 to 35% are lifetime abstainers. Drinking large amounts of alcohol (more than 2 to 6 drinks per day) for extended periods can damage a number of organs, especially the liver, heart, and brain. However, drinking a moderate amount of alcohol may reduce the risk of death from heart and blood vessel (cardiovascular) disorders. Nonetheless, drinking alcohol for this purpose is not recommended, especially when other safer, more effective preventive measures are available.

Alcohol Abuse

Most people do not consume enough alcohol or consume it often enough to impair their health or interfere with their activities. However, 7 to 10% of adults in the United States have a problem with alcohol use (alcohol use disorder). Disorders include at-risk drinking (defined solely by amount consumed), alcohol abuse, and alcohol dependence (the most severe alcohol use disorder). Alcoholism is an imprecise term. It typically refers to excessive drinking, unsuccessful attempts at stopping drinking, and continued drinking despite adverse social and occupational consequences. Men are 2 to 4 times more likely than women to become alcoholics.

Classifying Alcohol Use Disorders



At-risk drinking

Defined by the amount and frequency of drinking:

  • More than 14 drinks* a week or 4 drinks per occasion for men

  • More than 7 drinks a week or 3 drinks per occasion for women

Alcohol abuse

Drinking that does any of the following but without evidence of dependence:

  • Prevents people from fulfilling their obligations

  • Is done in physically dangerous situations (such as driving)

  • Results in legal, social, or interpersonal problems

Alcohol dependence

Frequent consumption of large amounts of alcohol causing more than three of the following problems:

  • People need to drink more and more alcohol to produce the same effects (tolerance).

  • Stopping the drug results in unpleasant, sometimes painful physical symptoms (withdrawal).

  • People drink more than they intended.

  • People want to reduce use but cannot.

  • People have spent a lot of time getting or drinking alcohol or recovering from its effects.

  • People have missed important events or activities (such as work, a wedding, or a graduation) because of drinking.

  • People continue to drink even though drinking is causing physical or psychologic problems.

*One drink is equivalent to 12 ounces of beer, 5 ounces of wine, or 1½ ounces of liquor, such as whiskey.

Generally, people who become alcoholics have been regularly using alcohol in excessive amounts for a long time and are dependent on alcohol. The amount of alcohol people consume on an average day before they develop alcohol problems varies widely. But it may be as little as 2 drinks per day for women and 3 drinks for men (one drink is equivalent to 12 ounces of beer, 5 ounces of wine, or 1½ ounces of liquor, such as whiskey). Many people with alcohol problems are also binge drinkers—that is, men who drink 5 or more drinks and women who drink 4 or more drinks per occasion. Binge drinking may go on for many days, followed by drinking little or none for a few days. Binge drinking is a particular problem among younger people.

Did You Know...

  • Drinking very large amounts of alcohol can quickly cause death.

Alcoholism leads to many destructive behaviors. Drunkenness may disrupt family and social relationships. Married couples often divorce. Extreme absenteeism from work can lead to unemployment. Alcoholics often cannot control their behavior, tend to drive while drunk, and experience physical injury from falls, fights, or motor vehicle accidents. Some alcoholics become violent. Alcoholism in men is often associated with domestic violence against women (see Violence Against Women).

Special Populations

Very young children who drink alcohol (typically accidentally) are at significant risk of very low blood sugar and coma. Women may be more sensitive to the effects of alcohol than men, even on a per-weight basis. Older people may be more sensitive than younger adults. Drinking during pregnancy increases the risk of fetal alcohol syndrome (see Alcohol).

Although sensitivity to the effects of alcohol may vary, people of all ages are susceptible to alcohol use disorders. Increasingly, adolescents are having alcohol problems, with especially disastrous consequences (see Substance Use and Abuse in Adolescents). Those who start drinking at an early age (particularly the preteen years) are much more likely to become dependent on alcohol as adults.


Alcohol use disorders involve heredity to some extent. Blood relatives of alcoholics are more likely to have alcohol use disorders than people in the general population, and alcohol use disorders are more likely to develop in biologic children of alcoholics than in adopted children. Some research suggests that people at risk of alcoholism are less easily intoxicated than people who are not alcoholics. That is, their brains are less sensitive to the effects of alcohol. Blood relatives of alcoholics may have this trait.

Certain background and personality traits may predispose people to alcohol use disorders. Alcoholics frequently come from broken homes, and relationships with their parents are often disturbed. Alcoholics tend to feel isolated, lonely, shy, depressed, or hostile. They may act self-destructively and may be sexually immature. Whether such traits are the cause of alcoholism or the result is not certain.


Alcohol causes three basic types of problems:

  • Those that occur immediately when people drink too much at a particular time (intoxication and overdose)

  • Those that occur over a long period of time when people regularly consume excessive amounts

  • Those that occur when heavy, long-term use is stopped suddenly (withdrawal)

Immediate Effects

Alcohol has almost immediate effects because it is absorbed faster than it is processed (metabolized) and eliminated from the body. As a result, alcohol levels in the blood rise rapidly. Effects can occur within a few minutes of drinking.

Effects vary greatly from person to person. For example, people who drink regularly (2 or more drinks per day) are less affected by a given amount of alcohol than those who normally do not drink or drink only socially, a phenomenon termed tolerance. People who have developed tolerance to alcohol may also be tolerant of other drugs that slow brain function, such as barbiturates and benzodiazepines.

Effects vary depending on the level of alcohol in the bloodstream, which is usually expressed in terms of milligrams per deciliter (1/10 liter of blood), abbreviated mg/dL. Actual blood levels required to produce given symptoms vary greatly with tolerance, but in typical users who have not developed tolerance, the following symptoms are typical:

  • 20 to 50 mg/dL: Tranquility, mild drowsiness, some decrease in fine motor coordination, and some impairment of driving ability

  • 50 to 100 mg/dL: Impaired judgment and a further decrease in coordination

  • 100 to 150 mg/dL: Unsteady gait, slurred speech, loss of behavioral inhibitions, and memory impairment

  • 150 to 300 mg/dL: Delirium and lethargy (likely)

  • 300 to 400 mg/dL: Often unconsciousness

  • 400 mg/dL: Possibly fatal

Vomiting is common with moderate to severe intoxication. Because people may be very drowsy, vomited material may enter the lungs (be aspirated), sometimes leading to pneumonia and death. Drinking large amounts can also cause low blood pressure and low blood sugar levels.

In most U.S. states, the legal definition of intoxication is a blood alcohol content (BAC) of 80 mg/dL or higher.

The effects of a particular blood level differ in chronic drinkers. Many seem unaffected and appear to function normally with relatively high levels (such as 300 to 400 mg/dL).

Long-Term Effects

Prolonged use of excessive amounts of alcohol damages many organs of the body, particularly the liver (alcoholic liver disease). Because people may not eat an adequate diet, they may also develop severe vitamin and other nutritional deficiencies.

Effects of Prolonged Alcohol Use

Type of Problem



Low folate (folic acid) levels

Anemia (fatigue, weakness, and light-headedness)

Birth defects

Low iron levels


Low niacin levels

Pellagra (skin damage, diarrhea, and depression)




Inflammation (esophagitis)



Inflammation (gastritis)



A bleeding tendency (coagulopathy)


Fatty liver

Inflammation (hepatitis)

Severe scarring (cirrhosis)


Inflammation (pancreatitis)

Low blood sugar levels (hypoglycemia)



Disturbance of the heart’s rhythm (arrhythmia)

Heart failure

Blood vessels


High blood pressure





Poor short-term memory (poor recall of recent events)

Psychosis (loss of contact with reality)

Reduced coordination


Deterioration of nerves in the arms and legs that control movements (reduced ability to walk)


Reproductive organs

Decreased sex drive

In men, enlarged breasts, smooth skin, and shrinking of the testes

Alcoholic liver disease includes liver inflammation (hepatitis), fatty liver, and cirrhosis (see Fibrosis and Cirrhosis of the Liver). An alcohol-damaged liver is less able to rid the body of toxic waste products, which can cause brain dysfunction (hepatic encephalopathy). People developing hepatic encephalopathy become dull, sleepy, stuporous, and confused and may lapse into a coma. Usually, they also have liver flap (asterixis): When the arms and hands are outstretched, the hands suddenly drop, then resume their original position. Liver flap resembles but is not a tremor. Hepatic coma is life threatening and needs to be treated immediately. With cirrhosis of the liver, pressure builds up in the blood vessels around the liver (portal hypertension—see Portal Hypertension). These blood vessels can bleed heavily, causing people to vomit blood. This bleeding is a particular problem because the damaged liver does not produce enough of the substances that make blood clot.

Excessive alcohol use can cause inflammation of the pancreas (pancreatitis). People develop severe abdominal pain with vomiting.

Excessive alcohol use can damage the nerves and parts of the brain. People may develop a chronic tremor. Damage to the part of the brain that coordinates movement (cerebellum) can lead to poorly controlled movement of the arms and legs. It can also damage the lining (myelin sheath) of nerves in the brain, resulting in a rare disorder called Marchiafava-Bignami disease. People with this disorder become agitated, confused, and demented. Some develop seizures and go into a coma before dying.

Severe alcoholism can cause a severe deficiency of thiamin, a B vitamin. This deficiency can lead to Wernicke’s encephalopathy (see Wernicke’s Encephalopathy), which, if not promptly treated, may result in Korsakoff’s syndrome (see Korsakoff’s Syndrome), coma, or even death.

Drinking alcohol may worsen existing depression, and alcoholics are more likely to become depressed than people who are not alcoholics. Because alcoholism, especially binge drinking, often causes deep feelings of remorse during dry periods, alcoholics are prone to suicide even when they are not drinking.

In pregnant women, alcohol use can cause severe problems in the developing fetus, including low birth weight, short body length, small head size, heart damage, muscle damage, and low intelligence or intellectual disability (mental retardation). These effects are called the fetal alcohol syndrome (see Alcohol). Avoidance of alcohol is therefore recommended during pregnancy.

Withdrawal Symptoms

If people who drink continually for a period of time suddenly stop drinking, withdrawal symptoms are likely. For example, withdrawal can occur during hospitalization (for example, for elective surgery) because drinkers are unable to obtain alcohol.

Withdrawal symptoms vary from mild to severe. Severe untreated alcohol withdrawal can be fatal.

Mild withdrawal usually begins 12 to 24 hours after drinking stops. Mild symptoms include tremor, headache, weakness, sweating, and nausea. Some people have seizures (called alcoholic epilepsy or rum fits).

Alcoholic hallucinosis may occur in heavy drinkers who stop drinking. They hear voices that seem accusatory and threatening, causing apprehension and terror. Alcoholic hallucinosis may last for days and can be controlled with antipsychotic drugs, such as chlorpromazine or thioridazine.

Delirium tremens (DTs) is the most serious group of withdrawal symptoms. Usually, delirium tremens does not begin immediately. Rather, it appears about 48 to 72 hours after the drinking stops. People are initially anxious. Later, they become increasingly confused, do not sleep well, have frightening nightmares, sweat excessively, and become very depressed. The pulse rate tends to speed up. Fever typically develops. The episode may escalate to include fleeting hallucinations, illusions that arouse fear and restlessness, and disorientation with visual hallucinations that may be terrifying. Objects seen in dim light may be particularly terrifying, and the people become extremely confused. Their balance is impaired, sometimes making them think the floor is moving, the walls are falling, or the room is rotating. As the delirium progresses, a persistent tremor develops in the hands and sometimes extends to the head and body. Most people become severely uncoordinated. Delirium tremens can be fatal, particularly when untreated.


Acute alcohol intoxication is usually apparent based on what people or their friends tell the doctor and on results of the physical examination. If it is not clear why a person is acting abnormally, doctors may do tests to rule out other possible causes of symptoms, such as low blood sugar or head injury. Tests may include tests to determine the amount of alcohol in the blood and the blood sugar level, urine tests for certain toxic substances, and computed tomography (CT) of the head. Doctors do not assume that simply because people have alcohol on their breath that nothing else could be wrong.

For legal purposes (for example, when people are in vehicle crashes or are acting abnormally at work), alcohol levels can be measured in the blood or estimated by measuring the amount in a sample of exhaled breath.

In people with a long-term alcohol use disorder, blood tests may be done to check for abnormalities in liver function and evidence of other organ damage. If symptoms are very severe, an imaging test such as CT may be done to rule out a brain injury or infection.

Screening for Alcohol Abuse

Some people may not know that their amount of drinking could be a problem. Others know but do not want to admit that they have an alcohol problem. Therefore, health care practitioners do not wait for people to ask for help. They may suspect an alcohol use disorder in people whose behavior changes inexplicably or whose behavior becomes self-destructive. They may also suspect an alcohol use disorder when medical problems, such as high blood pressure or stomach inflammation (gastritis), do not respond to usual treatment.

Many practitioners periodically screen people for alcohol-related problems by asking about their use of alcohol. Questions may include the following:

  • On average, how many days per week do you drink alcohol?

  • On a typical day when you drink, how many drinks do you have?

  • What is the maximum number of drinks you had on any given occasion in the past month?

If doctors suspect alcoholism, they may ask more specific questions about consequences of drinking, such as the following:

  • Have you ever felt you should cut down on your drinking?

  • Does criticism of your drinking annoy you?

  • Have you ever felt guilty about drinking?

  • Have you ever had an “eye opener” (a drink first thing in the morning) to steady your nerves or to get rid of a hangover?

Two or more “yes” answers to these questions indicate a probable alcohol problem.


Treatment may occur in the following situations:

  • People come because they do not want to continue drinking.

  • People are brought in because they have symptoms related to high blood alcohol levels.

  • People come because they have intolerable withdrawal symptoms. However, alcoholics who develop withdrawal symptoms usually treat themselves by drinking.

Emergency Treatment

Emergency treatment is needed when very large amounts of alcohol or alcohol withdrawal causes severe symptoms.

There is no specific antidote for acute intoxication. Coffee and other home remedies do not reverse the effects of alcohol. However, if people are in a coma, they may need to have a tube inserted in their airway to keep them from choking on vomit and secretions. If their breathing is suppressed, they may need to be placed on a ventilator.

If needed to prevent or treat dehydration or low blood pressure, fluids are given intravenously, and thiamin is given to prevent Wernicke’s encephalopathy. Often, doctors also add magnesium (which helps the body process thiamin) and multivitamins (for possible vitamin deficiencies) to the fluids.

For withdrawal symptoms, doctors often prescribe a benzodiazepine (a mild sedative) for a few days. It reduces agitation and helps prevent some withdrawal symptoms, seizures, and delirium tremens. Because people can become dependent on benzodiazepines, these drugs are used for only a short time. Antipsychotic drugs are sometimes given to people with alcoholic hallucinosis.

Delirium tremens can be life threatening and is treated aggressively to control the high fever and severe agitation. People are treated in an intensive care unit if possible. Treatment usually includes the following:

  • High doses of benzodiazepines, given intravenously

  • High doses of vitamins (especially thiamin)

  • Fluids given intravenously

  • Drugs that lower fever (such as acetaminophen)

  • Drugs that control heart rate and blood pressure

  • Treatment of complications (such as pancreatitis, pneumonia, and seizures)

With such treatment, delirium tremens usually begins to clear within 12 to 24 hours of its beginning, but severe cases may last for 5 to 7 days. Most people do not remember events during severe withdrawal after it resolves.

After any urgent medical problems are resolved, further treatment depends on how severe the alcohol use disorder is. If people have not become dependent on alcohol, doctors may discuss the serious consequences of alcoholism with them, recommend ways to reduce or stop their drinking, and schedule follow-up visits to check on how well they are doing.

For people with more severe disorders, a detoxification and rehabilitation program should be started.

Detoxification and Rehabilitation

In the first phase, alcohol is completely withdrawn, and any withdrawal symptoms are treated. Then alcoholics have to learn ways to modify their behavior. Without help, most alcoholics relapse within a few days or weeks. Rehabilitation programs, which combine psychotherapy with medical supervision, can help. People are warned about how difficult stopping is. They are also taught ways to enhance the motivation to stop and to avoid situations that are likely to trigger drinking. Treatment is tailored to the individual. These programs also enlist the support of family members and friends. Self-help groups, such as Alcoholics Anonymous, can also help.

Sometimes certain drugs (disulfiram, naltrexone, and acamprosate) can help alcoholics avoid drinking alcohol. However, drugs can typically help only if people are motivated and cooperative and if the drugs are used as part of an ongoing intensive counseling regimen. Results vary.

Disulfiram deters drinking because it interferes with alcohol metabolism, causing acetaldehyde (a substance that results from the breakdown of alcohol) to build up in the bloodstream. Acetaldehyde makes people feel ill. It causes facial flushing, a throbbing headache, a rapid heart rate, rapid breathing, and sweating within 5 to 15 minutes after people drink alcohol. Nausea and vomiting may follow 30 to 60 minutes later. These uncomfortable and potentially dangerous reactions last 1 to 3 hours. The discomfort from drinking alcohol after taking disulfiram is so intense that few people risk drinking alcohol—even the small amount in some over-the-counter cough and cold preparations or some foods. Disulfiram must be taken every day. If people stop taking disulfiram, its effectiveness in treating alcohol dependence is limited. Pregnant women, people who have a serious illness, and older people should not use disulfiram.

Naltrexone alters the effects of alcohol on certain chemicals made by the brain (endorphins), which may be associated with alcohol craving and consumption. This drug is effective in most people who take it consistently. A long-acting form can be given by injection once a month. Naltrexone, unlike disulfiram, does not make people sick. Thus, people taking naltrexone can continue to drink. Naltrexone should not be taken by people who have hepatitis or certain other liver disorders.

More Information

Wernicke’s Encephalopathy

Wernicke’s encephalopathy causes confusion, eye problems, and loss of balance and results from thiamin deficiency.

Wernicke’s encephalopathy is caused by a severe deficiency of thiamin, a B vitamin (see Wernicke’s Encephalopathy). In people who have only a small amount of thiamin stored in the body, it may be triggered by consuming carbohydrates.

Wernicke’s encephalopathy often develops in people with severe alcoholism because the long-term use of excess amounts of alcohol interferes with the absorption of thiamin. Also, alcoholics often do not consume an adequate diet and thus not enough thiamin. Wernicke’s encephalopathy may result from other conditions that cause prolonged undernutrition or vitamin deficiencies. These conditions include dialysis, severe vomiting, starvation, cancer, and AIDS.


Wernicke’s encephalopathy causes confusion, drowsiness, involuntary eye movements (nystagmus), partial paralysis of the eyes (ophthalmoplegia), and loss of balance. To maintain balance, people walk with their feet far apart and take slow, short steps.

Internal body processes may malfunction, causing tremor, agitation, a cold body temperature, a sudden and excessive decrease in blood pressure when people stand (orthostatic hypotension), and fainting. If untreated, Wernicke’s encephalopathy can lead to Korsakoff’s syndrome (see Korsakoff’s Syndrome), coma, or death. The combination is called Wernicke-Korsakoff syndrome.


Doctors suspect the diagnosis in people who have the characteristic symptoms and undernutrition or a thiamin deficiency, especially if they are alcoholics.

Tests, such as blood tests to measure blood sugar levels, a complete blood cell count, liver function tests, and imaging, are usually done to rule out other causes. Thiamin levels are not routinely measured.


The prognosis depends on how quickly the disorder is diagnosed and treated. Prompt treatment may correct all abnormalities. However, loss of balance and confusion may persist days to months. Without treatment, about 10 to 20% of people die.


Thiamin is given immediately by injection into a vein or muscle. It is continued daily for at least 3 to 5 days. Magnesium, which helps the body process thiamin, is also given by injection or by mouth. Fluids and multivitamins are given, and if levels of electrolytes (such as potassium) are abnormal, they are corrected. Some people may require hospitalization.

People with Wernicke’s syndrome must stop drinking alcohol. Thiamin supplements, taken by mouth, may need to be continued after the initial treatment.

Korsakoff’s Syndrome

Korsakoff’s syndrome (Korsakoff’s amnestic syndrome) causes memory loss for recent events, confusion, and apathy.

Korsakoff’s syndrome occurs in 80% of people with untreated Wernicke’s encephalopathy. Korsakoff’s syndrome is sometimes triggered by a severe bout of delirium tremens, whether Wernicke’s encephalopathy is present or not. Other causes include head injuries, stroke, bleeding within the brain, and, rarely, certain brain tumors.

People with Korsakoff’s syndrome lose memory for recent events. Memory is so poor that they often makes up stories, sometimes very convincingly, to try to cover up the inability to remember (called confabulation). They lose all sense of time. People become confused and apathetic and may not respond to events, even frightening ones. About 1 in 5 people with the syndrome do not completely recover. Some require care in an institution.

Doctors base the diagnosis on symptoms, particularly confabulation, in people with conditions that can cause Korsakoff’s syndrome.

Treatment consists of thiamin and fluids given intravenously. Thiamin supplements, taken by mouth, may need to be continued after the initial treatment.

Recovery depends on the cause. If the cause is a head injury or bleeding in the brain, people who are treated often improve. If the cause is Wernicke’s encephalopathy, the chances of recovery are worse: Only about 20% recover completely, and about 25% of people require institutional care. Improvement may take months and continue for up to 2 years or longer.

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