How Long Does Alcohol Stay In Your System?

When alcohol enters your system, your body will begin to metabolise it. Metabolism is the body’s chemical process for breaking down a substance to be absorbed or used as energy. This process happens when you consume any food or drink.

When you consume alcohol, the metabolising process is done primarily by your liver. On average, a person will metabolise the equivalent of one alcoholic drink per hour, but this can vary based on your weight, height, gender and body composition.

Read on to find out more about how long alcohol stays in your system, including parts of the body like blood, urine, saliva and hair.

How long does alcohol stay in the body?

Depending on how much you’ve consumed, the type of test used and some biological factors about the person drinking the alcohol, the amount of time the substance can be detected in your system can vary widely.

In general, a blood test can measure alcohol in your body for up to 6 hours after your last drink, while breathalyser tests work for between 12 and 24 hours. Urine tests, such as the ethyl glucuronide (EtG) test, are also effective for around 12-24 hours after use. This method tests for ethyl glucuronide, a breakdown product of ethanol – which is the alcohol you find in alcoholic beverages. Alcohol can also be detected in your hair follicles up to 90 days after consumption (source).

• Blood test – a blood test will show alcohol present in your bloodstream for up to 6 hours after your last alcoholic drink 
• Urine test – alcohol can be detected in your urine for approximately 12-14 hours after alcohol was last consumed
• Breath test - a breathalyzer can detect alcohol on the breath for approximately 12-14 hours after alcohol was last consumed
• Saliva test - alcohol can be detected in saliva for approximately 12-14 hours after alcohol was last consumed
• Hair test – traces of alcohol can remain in your hair and hair follicles for up to 90 after last consuming alcohol

How is alcohol measured in your body?

When you take a test that measures how much alcohol is in your system, it’s not the total amount of alcohol drunk that’s measured. Alcohol tests measure your blood/breath alcohol concentration (BAC) levels. Your BAC shows the amount of alcohol in your bloodstream or breath, shown by how much ethanol (in grams) is in 100 millilitres of blood or 210 litres of breath.

BAC can be used in breath, blood or urine tests, and is usually displayed as a decimal. One standard drink typically increases BAC levels by 0.02 in the 45-60 minutes it takes for your body to absorb the alcohol (source). One standard drink is the equivalent to:

• A can of 5% strength beer (12 fluid ounces)
• A small glass of 12% strength wine (5 fluid ounces)
• A single shot of 40% spirits, such as gin, whiskey or rum (1.5 fluid ounces)

On average, your body is able to absorb one standard drink every 60 minutes – reducing your BAC levels by around 0.16. So, if you consume an alcoholic drink every hour, your BAC levels will continue to increase. 

What impacts how long alcohol stays in your system?

Many factors impact how long alcohol remains in your system, not least the amount of alcohol you have consumed. Some of the other things that might affect how long it takes your body to metabolise alcohol include:

• Gender: Generally, women have a higher percentage of fat and a lower percentage of water in their bodies than men. This isn’t true of everyone, but it can lead to alcohol staying in a woman’s system for longer
• Food: Alcohol is absorbed in your digestive tract, so the presence of food makes this process slower – leading to alcohol staying in your system for longer. However, it does help to reduce the feelings you get from drinking alcohol i.e. how ‘drunk’ you feel
• Body composition: People with smaller body frames are likely to have higher levels of BAC from the same amount of alcohol as someone who is taller than them, due to the higher concentration of alcohol in smaller bodies
• Medication: Some medications, such as antidepressants and antibiotics, can affect how your body processes alcohol. Always consult your doctor for advice if you plan to consume alcohol while using medication

How long does it take to feel the effects of alcohol?

Once you’ve had an alcoholic drink, you’ll likely start to feel the effects within just a few minutes. Alcohol starts to absorb in your stomach and small intestine very quickly after consumption. From there, it travels into your bloodstream, which then transports it across your entire body. When transported to the brain, alcohol can impair messages being made there, affecting your emotions, movement and senses.

The factors that impact how long alcohol stays in your system are at play again here. Body composition, your gender, if you’ve recently eaten and any medication you’re taking can all influence how quickly, and how severely, you feel the effects of alcohol once you’ve consumed it.

When does it become alcoholism?

In small amounts, alcohol can be enjoyed as part of a healthy, balanced lifestyle. However, for some, alcohol consumption can spiral out of control, leading to a dependence on the substance. If you’re concerned about how much alcohol you or someone you know is consuming, here are some of the key signs of alcohol addiction to look out for:

• Developing a stronger tolerance to alcohol, meaning that you need to drink increasingly higher amounts of alcohol in order to feel ‘drunk’
• Drinking at inappropriate times such as first thing in the morning
• Headaches caused by dehydration
• Secretive or dishonest behaviour
• Drinking heavily alone
• Drinking to the point of passing out
• Other struggles with mental health such as depression and anxiety