Over the past few years we have seen a steady increase in the amount of clients charged with drink driving the morning after they drank.

This is in part because of extra testing now carried out by the police in the mornings and also people's lack of knowledge on how alcohol is absorbed by the body while they are asleep.

Why are there an increasing drink driving charges for drinking the night before?

There is of course no way in which you can accurately know how much alcohol is in your system. Portable drink driving testers will give a general indication but could never be relied on to give inaccurate sample. Even the police when conducting tests use their portable breath test only as an indication that a person might be over the legal limit, they still require specialised equipment to find out the exact amount of alcohol in the system.

Perhaps the greatest reason for the increase we have seen with clients charged drink driving in the morning is an inaccurate idea of when a person is below the legal limit.

Alcohol absorption while sleeping

Alcohol metabolism is the process by which the body breaks down the ethanol in alcohol. Liver cells produce the enzyme alcohol dehydrogenase which breaks alcohol into ketones. Nothing will speed up the rate of detoxification, but the effective metabolism of alcohol can be limited by sleeping.

Ethanol is readily soluble in water, so it easily dissolves in the bloodstream and gets carried to various parts of the body. The most affected areas of the body include the liver and the brain (see this study).

Once alcohol is in the bloodstream, it can only be eliminated by the enzyme alcohol dehydrogenase through sweat, urine, and breath. Drinking water and sleeping will not speed up the process. Coffee, energy drinks, or a cold shower will not sober you up faster they will just make you feel more awake and mask the effects of the alcohol.

Everyone's oxygen levels in the blood are lower during sleep.  Therefore it is theorised that as a sleeping person does not need as much oxygen as an awake person then the level of metabolism of ethanol reduces whilst asleep.

Other potential factors slowing the metabolism of alcohol include;

1. Slower gastric emptying: Alcohol slows down the rate at which your stomach empties its contents into the small intestine. During sleep, the rate of gastric emptying naturally decreases, which can further slow down alcohol absorption.
2. Reduced metabolic rate: While asleep, your body's metabolic rate tends to be lower compared to when you're awake. This slower metabolism affects the breakdown of alcohol in the liver, potentially leading to a longer duration of alcohol in your system.

However, it's important to note that even while you sleep, alcohol continues to be processed and eliminated by your liver and other bodily functions. The rate at which this occurs depends on various factors, including the amount of alcohol consumed, your body weight, metabolism, and individual differences.

How fast can you sober up?

Alcohol leaves the body at an average rate of 0.015 g/100mL/hour, which is the same as reducing your BAC level by 0.015 per hour.

Factors that affect the absorption rate include sex, body size and food intake therefore the .015 level is just a very general guide.

Example: At an average rate of -0.015/hr, how long would it take someone with a BAC of 0.20 to sober up?

According to the Bowling Green State University

What do we make of this?

While it’s an interesting that there is a scientific basis for the fact you sober up slower while sleeping what we tend to find is people simply don’t realise how long it takes to sober up and often wake up and feel ok to drive home or to work not realising it can take many hours to get below .05

Giving the increasing amount of people charged with drink driving in the morning it is likely the police will continue to undertake testing in the morning and that trend will therefore likely continue to rise into the future.

This article is obviously not written by a medical professional just a drink driving lawyer who has represented over a thousand people charged with drink driving in Queensland and is therefore based on my observations and conversations with my clients over the years.

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