What is BAC?
Blood alcohol content (BAC), also known as a blood alcohol level, is the amount of alcohol in your blood. Levels can range from 0% (no alcohol) to over 0.4% (a potentially fatal level).
Why does my BAC matter?
According to the National Health and Medical Research Council, even very small amounts of alcohol can affect your concentration, judgement, and performance. You may feel like you’re ok, but your reaction times will be slower than normal, and your concentration will be reduced.
This makes it difficult to perform activities that require skill and concentration, or where the safety of others is involved. For example, driving, flying, water sports, skiing, using complex or heavy machinery, or farm machinery.
Read more below how your BAC level matters in driving and working legally.
How to read Blood Alcohol Concentration (BAC)?
BAC can be used as a guide to what effects alcohol may have on behavior. People who drink alcohol regularly may show less effect at higher BAC. Here’s a brief guide from SA Health on how each level likely affects an individual’s behavior.
- A BAC of up to 0.05 g% is likely to cause a feeling of wellbeing. Likely effects are being talkative, more relaxed and more confident.
- A BAC of 0.05 to 0.08 g% is likely to make you at risk of impaired judgment and reduced inhibitions.
- A BAC of 0.08 to 0.15 g% is likely to put you in a risky state. Likely effects include slurred speech, impaired balance and coordination, unstable emotions and possibly nausea and vomiting.
- A BAC of 0.15 to 0.30 g% will put you at high risk with likely effects to be inadequate breathing, unable to walk without assistance, loss of bladder control and possibly loss of consciousness.
- A BAC of over 0.30 g% is likely to put you in a coma or result in death.
- A BAC 0.05% and above significantly increases the risk of car crash and fatality, according to World Health Organization
How is BAC measured?
Blood alcohol concentration can be measured with a breathalyser, or by analysing a sample of blood, saliva, or urine.
What is the legal BAC in Australia?
In Australia, it is an offence to drive while your BAC is 0.05 or above*.
Your BAC should remain below 0.05 if you: drink no more than two standard drinks in the first hour and one per hour thereafter (for men of average size); or. drink no more than one standard drink per hour (for women of average size), as said by the WA Police Force.
Note: If you’re on a learners or provisional licence, your BAC must be zero. More info below.
How do I stay below 0.05?
There’s no amount of drinking that guarantees you’ll stay under 0.05% BAC.
It generally takes the body about 1 hour to process 1 standard drink. However, two people can drink the same amount of alcohol and have different BACs. This is because there’s a range of individual factors that affect how alcohol is broken down and absorbed, as stated in Australian Guidelines to Reduce Health Risks from Drinking Alcohol 2020.
Check out this Drinking Calculator to find out how your drinking measures up against the World Health Organization's international risk assessment tool.
What affects my BAC?
According to ADF, your blood alcohol levels can be influenced by:
- body size
- how much you have eaten
- body fat percentage
- liver health
- age
- sex
- alcohol tolerance
- medications
- the strength of your drinks
Drinking and Driving
In Australia, it’s illegal to drive if your blood alcohol level is over 0.05%.
If you choose to drink, consider different transport options - public transport, rideshare or organising a friend to be a designated driver.
Note: You must have a 0.00% BAC in most Australian states or territories if you are a:
- learner, provisional, or probationary driver – regardless of age
- truck driver
- bus driver
- driving instructor or if you are supervising a learner driver
- convicted of driving under the influence (DUI).
Warning! Even if you’re below 0.05% BAC, your judgement, reaction times and driving skills are impacted.
Drinking and working
Blood alcohol limits apply in jobs like flying planes (e.g. no alcohol within 24 hours of flying), driving public or heavy vehicles, operating commercial ships or machinery. In these jobs, the BAC limit is zero (0.00%). If you’re unsure what your employer’s required BAC limit is, make sure you find out before getting behind the wheel.
Some workplaces implement alcohol and drug testing as a protocol. You can be tested as part of pre-employment screening, at random or following an incident in the workplace.
Workplaces usually only enforce alcohol testing when they are legally obligated to, or where employers, workers and unions agree it’s necessary.
Make sure to read your employment agreement and company policies to check what your obligations and rights are.
