How Long Does Alcohol Stay in Your System?

It takes the body around an hour to metabolise one unit of alcohol. However, the amount of time it takes the body to break down alcohol is influenced by a number of factors.

These factors either slow down or speed up the amount of time it takes the body to metabolise alcohol.

Knowing how long it takes alcohol to be metabolised in your body allows you to roughly track the level of alcohol in your system.

This helps you to prevent alcohol intoxication.

In this post, we shall look at these factors.

Factors influencing the speed in which alcohol is metabolised in the body

Below, we list a number of factors that affect the amount of time it takes your body to break down alcohol.

These factors include:

• Your age
• Your weight
• Your sex
• The amount of food you have eaten when you drink alcohol
• Your metabolism (the speed at which your body converts food into energy
• Medications you may be taking
• The health of your liver

Testing for alcohol in your system

The amount of alcohol contained in your system is known as the blood alcohol concentration (BAC). To detect alcohol in your system, a number of methods are employed. For instance, to detect alcohol in your breath, a Breathalyser is used. To detect alcohol in your urine, a urine sample will be taken.

The type and amount of alcohol your drink

The amount of time it takes your body to rid itself of alcohol is also influenced by the amount and type of alcohol you drink. If you drink a pint of whisky, the body will surely take longer to process this vast amount of alcohol compared to drinking a pint of weak lager.

The amount of alcohol contained in a drink is measured by units. One unit of alcohol equates to 10ml of pure ethanol.

Below, we list the number of units contained in common measurements of alcohol served in bars, pubs and restaurants throughout the United Kingdom.

• A standard glass of wine (175ml) contains 2.1 units of alcohol
• A large glass of wine (250ml) contacts 3 units of alcohol
• Weak beer (3.6% proof) contacts 2 units of alcohol
• Strong beer (5.2% proof) contains 3 units of alcohol
• A single shot (25ml) contains 1 unit of alcohol

As stated above, it roughly takes one hour for the body to metabolise one unit of alcohol. During a drinking session, it makes sense to count the number of drinks you consume. This will allow you to calculate the amount of time it takes your body to metabolise this precise amount of alcohol. If you drink a 750ml bottle of wine, you will have consumed 9 units of alcohol. It will thus take your body 9 hours to fully metabolise this amount of alcohol.

A word of warning

Please add an additional two hours to this rough calculation in regards to the amount of time it takes your body to metabolise alcohol. Why? Because the above is only intended to serve as guidelines. The amount of time it takes your body to break down alcohol is affected by a number of different factors listed above. Adding an additional two hours to the above ensures your body has been permitted enough time to eliminate all alcohol toxins from your body before you, for instance, attempt to drive a vehicle or operate heavy machinery.

If you must drive a vehicle the following day after a drinking session, then we advise you limit your drinking to 2-3 units. This ensures you will not still have alcohol in your blood when you drive.

Drinking guidelines

Alcohol is a toxin. When you expose your body to alcohol, you risk harming your health in a number of ways. To encourage people to drink moderately, the Government has published drinking limitation guidelines. These guidelines advise women and men not to drink more than 2 units a day, and no more than 14 units over the course of a week.

Alcohol in urine

Generally speaking, alcohol remains in urine and it is detectable in a urine test for around 12-36 hours following consumption. Some advanced urine tests may detect alcohol in the urine for a period up to 80 hours after consumption.  Urine testing (urinalysis) detects the metabolites formed when alcohol is broken down in the liver.

Alcohol in the breath and hair

Urinalysis to detect alcohol involves an expensive procedure, so law enforcement agencies prefer to test for alcohol consumption in the breath and saliva using a Breathalyser. A Breathalyser may detect alcohol in the breath for around 24 hours following consumption.  

An alternative means of testing for alcohol consumption is by way of a hair follicle test.  This will reveal alcohol consumption for up to 90 days following consumption. Like the urine test, a hair follicle test is expensive and thus rare in practice.

How is alcohol broken down in your body?

When you drink alcohol, it passes through your digestive system. However, alcohol is not digested because much of it is absorbed into the bloodstream. From the blood, alcohol is then filtered and then broken down in the liver.  Around 20% of alcohol you consume passes into the blood vessels.  The remaining 80% of alcohol that’s not absorbed directly through blood vessels is nevertheless absorbed into the bloodstream through the small intestine.

Alcohol then passes through the body in the bloodstream. Alcohol reaches the brain where it stimulates a number of neurotransmitters such as GABA-A and dopamine. The stimulation of these neurotransmitters explains the pleasurable effects we experience when alcohol is consumed.

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