The level of alcohol in the blood is measured as the blood alcohol concentration (BAC). A BAC of 0.01 means there is one gram of alcohol in 100 millilitres of blood. In Australia, one standard drink contains 10 grams of alcohol. In an average healthy person, one standard drink increases the BAC by about 0.02 and takes approximately one hour to break down. The more alcohol that is consumed, the higher the BAC. Even after ceasing to drink, the BAC can keep rising. The only way to lower the BAC is by giving the body time to break down the alcohol.

In Australia, it is an offence to drive a vehicle while the BAC is 0.05 or higher. To stay below this limit, men are advised to drink no more than two standard drinks in the first hour and one drink per hour after that. Women are advised to drink no more than one standard drink per hour. However, this is a general guide only, as the BAC is influenced by a range of factors including body size, metabolism rate and how often alcohol is consumed.

The National Health and Medical Research Council (NHMRC) provides advice to Australians to help them make informed choices about drinking alcohol. In 2020, the NHMRC released revised guidelines about alcohol consumption.

The guidelines are as follows:

The NHMRC defines ‘risky alcohol consumption’ as drinking more than 10 standard drinks per week on average or having more than four standard drinks in a single day at least once a month over a period of 12 months.

Alcohol is associated with a range of harms.

Short-term risks include:

• Increased risk of experiencing an accident or injury; for example, through road traffic accidents, falls, fires and drowning (this risk is especially high among young people).

• Increased risk of sexually transmitted infections (STIs) or unintended pregnancy.

• Increased chance of experiencing and/or perpetrating violence; for example, getting into fights or being assaulted.

Longer-term risks:

• Alcohol dependence

• Brain damage and problems with brain development 

• Malnutrition

• Cardiovascular (heart) problems

• Cancer – alcohol has been linked to a range of cancers, including mouth, oesophagus, liver and breast cancers

• Liver problems

• Mental health problems, such as anxiety and depression

• Complications in those with diabetes and/or obesity

• Fetal Alcohol Syndrome in people who were exposed to alcohol during gestation.

The day after consuming alcohol a person may experience a hangover. The effects of a hangover can include:

• Headache

• Diarrhoea and nausea

• Tiredness and trembling

• Increased heart rate and blood pressure

• Dry mouth

• Trouble concentrating

• Anxiety

• Poor or decreased sleep.

Sobering up from alcohol takes time. The liver gets rid of about one standard drink an hour. Sweating it out with exercise, cold showers, coffee, fresh air or vomiting will not speed up the process.

If drinking continues for an extended period, bodily functions can shut down and a person may lose consciousness. This is called alcohol poisoning and it can lead to death. This can happen if an individual stops breathing, or by suffocation if a person vomits while unconscious as well as through interactions with other drugs.

The combined effects of drinking alcohol and taking other drugs, including over the counter or prescription medications, increases the overall risk of harm. As alcohol depresses brain activity, it should not be used with other drugs or medications that have similar effects on the brain, particularly benzodiazepines and heroin. Mixing alcohol with other depressants can result in breathing difficulties and overdose.

Sudden withdrawal from long-term, heavy alcohol use can be life threatening. Withdrawal symptoms can start within a few hours after the last drink and can continue for between two and seven days.

Symptoms include:

• Sweating

• Tremors (delirium tremens)

• Nausea

• Anxiety, irritability, difficulty sleeping

• Seizures or fits

• Delusions and hallucinations

• Death.

There are strong associations between alcohol problems and affective disorders such as depression, bipolar disorder, and anxiety disorders. The use of alcohol can make the symptoms and prognosis of mental illnesses worse. In 2022-23, people experiencing high or very high levels of psychological distress were more likely to consume alcohol in ways that puts their health at risk.

There are a number of options to treat dependent use of alcohol. Simply ‘detoxing’ alone does not constitute adequate treatment, and other measures are required to prevent relapse.

Treatment options include:

• Detoxification - the primary aim is to manage withdrawal syndrome and interrupt the pattern of chronic and heavy use. Detoxification may be aided by pharmacotherapy. Withdrawal can be life-threatening, so appropriate medical supervision and monitoring is required.

• Residential rehabilitation (RR) and 12-step programs (e.g., Alcoholics Anonymous) - these are frequently used for the treatment of alcohol dependence, with most based on the ‘12-step model’. It may be for a period of one to 12 months and can include vocational rehabilitation and other onsite support services, such as legal, medical and mental health. Therapeutic communities (a sub-class of RR) are also based on the 12-step model and are often associated with support groups like Alcoholics Anonymous (AA).

• Psychological interventions - clinically effective psychological interventions include cognitive behavioural therapy, motivational enhancement, contingency management, and social and family support services.

• Pharmacotherapy - several medications are used to treat alcohol addiction, including naltrexone, disulfiram and acamprosate.

According to the Australian Institute of Health and Welfare (AIHW), one in three people drink alcohol in ways that put their health at risk. In 2020, the NHMRC updated its guidelines to reduce alcohol-related harms. Despite this, the proportion of people in Australia who drink alcohol at risky levels has not changed between 2019 and 2023-23.

The AIHW survey also showed that, in 2022-23, men are more likely to drink at risky levels compared to women. However, the current rate of men drinking at risky levels follows a long-term decline from 50% in 2007 to 39% in 2022–2023. A similar trend occurred among females, but the change was much more gradual (from 27% in men (up from 35% in 2019).

The Illicit Drug Reporting System (IDRS) is an Australian monitoring system run by the National Drug and Alcohol Research Centre (NDARC) at UNSW Sydney that identifies emerging trends of local and national concern in illicit drug markets.

The Ecstasy and Related Drugs Reporting System (EDRS) is an Australian monitoring system run by NDARC that identifies emerging trends of local and national interest in ecstasy and related drug use, markets and harms.

The Pocket Guide to Drugs and Health is a publication authored by experts from NDARC that provides information for health professionals on the impact of drug use.

The Australian Institute of Health and Welfare collects information on alcohol and tobacco consumption, and illicit drug use among the general population in Australia.

The Australian Bureau of Statistics is Australia’s national statistical agency, providing official statistics on a range of economic, social, population and environmental matters of importance to Australia.

Alcohol and Drug Foundation (2023). Alcohol. Retrieved from: adf.org.au/drug-facts/alcohol/

Alcohol and Drug Foundation (2022). Blood Alcohol Levels. Retrieved from: adf.org.au/insights/blood-alcohol-levels/

Australian Government Department of Health and Aged Care (2022). What are the effects of alcohol? Retrieved from: health.gov.au/topics/alcohol/about-alcohol/what-are-the-effects-of-alcohol

Australian Institute of Health and Welfare (2024). Mental health and use of alcohol, tobacco, e–cigarettes and other drugs. AIHW, Australian Government. Retrieved from: aihw.gov.au/reports/mental-health/mental-health-alcohol-drugs

Darke, S., Lappin, J., & Farrell, M. (2024). The Clinician’s Guide to Illicit Drugs and Health (Revised Edition); London: Silverback Publishing.

National Health and Medical Research Council (2020). Australian Guidelines to Reduce Health Risks from Drinking Alcohol. Commonwealth of Australia, Canberra. Retrieved from: nhmrc.gov.au/about-us/publications/australian-guidelines-reduce-health-risks-drinking-alcohol