After alcohol is ingested, it immediately starts to enter the blood stream. Alcohol in the body continues to be absorbed until alcohol concentrations in the blood are high enough to make alcohol available for elimination.  It takes an average of an hour and a half for this process to occur in healthy adults who have not eaten within two hours of consuming alcohol.

Once alcohol has entered the bloodstream, enzymes in the liver metabolize alcohol into acetaldehyde with 10 percent being eliminated unchanged via lungs or sweat glands.  The rate of alcohol elimination in humans is about one drink per hour regardless of sex, weight, race, or food intake. Metabolism varies between people based on genetics, medications taken, health conditions present, and alcohol tolerance.  Alcohol elimination in men is faster than women because alcohol dehydrogenase, an enzyme that breaks down alcohol in the stomach, is present in higher concentrations in men.

The rate at which alcohol is eliminated from the body varies greatly between individuals as well as gender and age differences. Despite individual variations, alcohol can be usually expected to be eliminated from a person's system within three or four days.

How Long Does Alcohol Stay in Your Body?

Alcohol is metabolized [transformed] by the body at a fairly steady rate [however, there are factors that can speed up alcohol metabolism]. In general, alcohol will be eliminated from the human body at a rate of approximately 1/3rd an ounce per hour. However, this does not mean that alcohol cannot be found in the blood or urine after one hour has passed; rather it means that alcohol will be reduced to 1/3rd its concentration every hour. As for how long alcohol stays in your system, well alcohol can usually be found anywhere between 2-5 hours afterwards, depending on several different factors. The most important factor is the amount of alcohol consumed. Someone who just had a couple of drinks will have lower alcohol concentrations in their blood, urine and breath than someone who has consumed the equivalent amount in alcohol.

Individual Factors to consider when determining alcohol elimination times:

1) Gender & Weight:

Females are more sensitive to alcohol's toxic effects because they generally weigh less than males with similar body composition. As such, they typically achieve higher alcohol concentrations in the bloodstream for any given dose of alcohol.

2) Age:

As one age, there is a general decrease in lean body mass which leads to an average loss of 1% per year after the age of 25 years old. This leads to slower alcohol metabolism rates as well as delayed accumulation rates during prolonged alcohol consumption. 

3) Food Consumption:

Having food in your system can decrease alcohol metabolism by nearly 50%. The time course of alcohol elimination is also delayed, with peak alcohol levels being seen later. This means that alcohol will stay in your system for longer if food is consumed along with alcohol - this includes having a full stomach or eating shortly before or after drinking alcohol.

4) Hydration Status:

Alcohol consumption causes an initial diuresis followed by a state of retention during steady-state alcohol concentrations; This leads to dehydration which slows alcohol metabolism down by 15-20%.

5) Race:

Asian Americans have been found to have one of the lowest rates of alcohol metabolism, leading to higher average BACs and prolonged effects relative to other races/ethnicities.

6) Medications:

Alcohol can increase or decrease the rate of elimination of over 562 medications being taken in the USA. Prescription and non-prescription drugs can alter alcohol metabolism rates, which means that alcohol will stay in your system for longer if you are taking some sort of medication.

7) Stress:

Stress is known to increase alcohol's toxic effects by inhibiting enzymatic [chemical] alcohol metabolism via the liver. This increases the toxicity of alcohol itself while also lengthening alcohol stay in your system. 

8) Smoking:

Nicotine has been found to increase alcohol elimination by 30%. This is because nicotine reduces hepatic blood flow leading to more rapid intoxication with lowered alcohol levels.

9) Obesity:

Being obese can increase alcohol-related diseases & death due to alcohol consumption, leading to longer alcohol stay in your system. 

10) Alcohol Use Disorder (Abuse or Dependence):

People who suffer alcohol use disorder experience greater alcohol-related problems compared to social drinkers. This includes increased alcohol metabolism rates due to elevated alcohol elimination; However, they also tend to have more fat deposits in the liver which can lead to slower alcohol elimination times.

11) Developmental Factors:

Teenagers who are below the legal drinking age of 21 have been found to have a delayed alcohol metabolism rate as well as decreased body water content. This leads to lower alcohol concentrations and a later peak time compared to those over the legal drinking age. 

12) Chronic Drinking:

Individuals who chronically abuse alcohol will show accelerated alcohol metabolism due to both increased alcohol elimination as well as alcohol induced liver enzyme production. This leads to alcohol stay in your system being significantly shortened for chronic alcohol abusers relative to casual drinkers.