Alcohol stays in your system for up to;
Different Tests Detect Alcohol In The Body For Different Durations
A blood alcohol concentration test [BAC] is used to see if drinking alcohol has occurred in the last 12 hours .
It also detects how much alcohol has been drunk, with 80mg per 100 mg of blood being over the legal alcohol limit .
Urine tests indicate alcohol use up to 48 hours after the last drink, but cannot indicate how much alcohol has been consumed .
Hair tests indicate alcohol use up to ninety days after the last drink, but cannot indicate how much alcohol has been consumed .
Saliva tests detect alcohol consumption up to 48 hours after alcohol abuse .
Inaccurate or false positive test results may occur when there has been use of products containing alcohol, such as hand sanitiser or mouthwash .
Inaccurate test results may also occur if tests are not sealed correctly or remain at room temperature too long before being analysed, as this causes bacteria to build up and EtG levels to rise .
Alcohol Retention Rate Variables
Women have higher BAC levels than men despite drinking the same amount of alcohol .
Those with higher percentages of body fat are slower to absorb alcohol than those with lower percentages.
Women typically have higher percentages of body fat than men .
Taking aspirin increases the absorption of alcohol into the bloodstream, causing higher BAC levels .
Those drinking without eating previously will hit a peak BAC between 30 minutes to 2 hours; those who have eaten will hit a peak BAC between 1 to 6 hours .
Emotions such as depression, anxiety and anger may cause a change in enzymes in the stomach, increasing the absorption of alcohol .
Dehydration caused from vomiting, diarrhoea and kidney failure causes higher BAC rates after alcohol abuse  .
Liver disease or cirrhosis stops the liver from being able to flush out alcohol from the body, leading to higher BAC levels .
Ethnicity and Genetics
1 in 3 people with East Asian heritage develop facial flushing after drinking alcohol; due to a genetic deficiency of aldehyde dehydrogenase, causing higher blood alcohol concentration .
Those with a family history of alcohol use disorder may develop a higher tolerance to alcohol, causing higher consumption of alcohol and higher blood alcohol concentration .
How Long One Alcoholic Drink Stays In Your System
The breakdown rates of spirits, beer and wine in the table below are indicative of it being the first drink consumed, there being no medical, genetic or gender variables causing higher BAC and not suffering from alcohol use disorder.
How long would one measure of alcohol take to leave your system?
Alcohol Retention In Casual, Binge, And Long Term Drinking Patterns
Long Term Drinking
How long does each drinking pattern take to be absorbed by the body?
How Do I Know If Alcohol Is Still Present In My Body?
Studies have shown that a 10% increase in breath alcohol concentration equates to a 2% increase in reaction time .
A BAC calculator checks your gender, the amount of alcohol that has been consumed over a time period and body weight to calculate the amount of alcohol remaining in the body .
Studies have found that some drinkers have alcohol still present in the body without presenting any physical symptoms of being drunk, so a breath test or BAC calculator is the only way to be certain that alcohol has left the body .
Prolonged alcohol misuse, pre- existing fatty liver disease, and liver cirrhosis cause the liver to stop regenerating, leading to higher amounts of alcohol in the system .
Exceptions That Change How Long Alcohol Stays In The Body
Alcohol that is mixed with water or fruit juice is absorbed more slowly by the body, whereas alcohol mixed with fizzy drinks is absorbed more quickly .
Cough syrups and laxatives may contain up to 10% alcohol, adding to and prolonging the time that alcohol will stay in your system .
Auto brewery syndrome occurs when the body turns carbohydrates into alcohol, leading to high BAC levels after only small amounts of alcohol have been consumed .
Studies have suggested that consuming alcohol alongside activated charcoal may increase how quickly the body processes alcohol .
... Does Not Mean Alcohol Is No Longer In The Body
Feeling drunk vs alcohol being physically detectable by testing
Due to functional tolerance, those in active alcohol addiction may not feel drunk, but will still have blood alcohol levels that are physically detectable by testing .
Hangover vs alcohol being physically detectable by testing
Hangovers typically begin when BAC is at 0, and therefore do not occur when alcohol is physically detectable by testing .
Withdrawal vs alcohol being physically detectable by testing
Withdrawal symptoms will only occur when detectable alcohol levels in those with chronic alcohol addiction have reduced; those with less severe alcohol abuse issues will not have detectable alcohol levels when withdrawal occurs .
How Long Alcohol Stays In The Body Is Not Determined By...
What You Eat
There is a belief that eating a big breakfast after a night of alcohol consumption will cause the body to metabolise alcohol faster. In fact, food causes alcohol to be metabolised more slowly .
It is a myth that coffee or energy drinks speed up how long alcohol can stay in your system, as caffeine has no effect on the alcohol metabolism by the liver .
Some believe that vomiting purposefully after drinking lowers BAC, but as alcohol quickly moves to the blood stream, removing alcohol from the stomach and small intestines does not make a difference to BAC test results .
There is a myth that a cold shower will cause alcohol to leave the body, but there is no scientific evidence of this .
Whilst sleep allows time for the body to rest and for the liver to deal with the alcohol consumed, it doesn't increase how quickly the body can process alcohol .