The Science of Blood Alcohol Levels: Alcohol Absorption & Elimination


Blood alcohol levels are related to the amount of alcohol consumed. The passage of time may mean that some of the alcohol has been eliminated from the body.  A person charged with drunk driving invariably be asked these questions which pertain to the science of alcohol absorption and elimination from the blood:

  • How many drinks were consumed (see below: 80 proof 1.5 ounce shot = 12 ounce 5% alcohol beer = 5 ounce glass of wine)?
  • What was the alcohol percentage or proof of the beverage consumed?
  • How big were the alcohol containers/glasses, shot, 12 oz, 16 oz?
  • Did any of the beverages involve a higher than usual alcohol content (designer beers, hard liquor such as Everclear can be up to 190 proof)?
  • What time did drinking begin and when was the last alcoholic beverage consumed?
  • What was the result of the test administered by the police (breathalyzer) which measures blood alcohol content (BAC)?
  • How much time elapsed from the time that the last alcoholic beverage was consumed until the time that the blood alcohol test was administered by the police?

The answers to these questions, and others, allow our Macomb County DUI attorneys to explore the accuracy of the chemical or blood test result which measures blood alcohol content (BAC) and explain the processes of alcohol absorption and elimination to our prospective clients. This article contains a description of these processes along with various useful charts.

Alcohol absorption and elimination are processes that occur when a consumes an alcoholic beverage. Absorption refers to the passage of alcohol through the blood, while alcohol elimination is the rate at which alcohol leaves the body.

Blood alcohol content

Shot, Beer, and Wine

Blood alcohol content (BAC), or blood alcohol level (BAL), refers to the amount of alcohol in the body. Numerous factors have an influence on BAC levels. These include consumption of food, percentage of alcohol, body weight, sex, and physical activity. Furthermore, every person digests alcohol in a different way, which leads to varying absorption and elimination rates.

Alcohol absorption

Through a process known as diffusion, alcohol is absorbed through the stomach and small intestine. The rate of absorption occurs more rapidly when a person consumes a beverage with a higher proof, or percentage of alcohol.

Absorption occurs faster when a person drinks alcohol on an empty stomach because the alcohol goes directly into the stomach lining, without a barrier of food. An individual may attempt to control alcohol absorption by slowing down the ingestion of alcoholic beverages and by drinking water in between alcoholic beverages. It should be noted that recently consumed alcoholic beverages would not necessarily show up on a breath test because the process of absorption takes time to occur.

Ordinarily, it takes about 30 to 60 minutes for alcohol to be absorbed in the body. However, it may take up to two (2) hours for complete absorption to occur when someone engages in binge drinking within a short period of time. Binge drinking refers to an individual’s consumption of multiple alcoholic beverages in two hours. Generally, the amount of drinks per two hours varies between men and women; men must consume five (5) or more drinks, while women must only consume four (4) or more drinks to meet the level of binge drinking.

Alcohol elimination

Alcohol is eliminated from the body via excretion and metabolism.  Most alcohol is metabolized, or burned, in a manner similar to food; this process results in production of carbon dioxide and water. A small portion of alcohol is excreted through the individual’s breath, leaving the body as alcohol. This process allows for a breath alcohol test, or more commonly referred to as a Breathalyzer test.

Average rate of elimination


First, it must be understood that everybody eliminates alcohol from his or her bloodstream at different rates. The factor playing the most significant role in the elimination of alcohol is the passage of time. Over time, alcohol is eliminated from the body in the same manner that other toxins are eliminated. Scientific studies, however, have been able to ascertain an average rate of elimination for individuals. According to Forcon, a well-known forensic consulting firm, individuals may see a decrease in their BAC by 10-20% within the first hour, while most will only see a 13-18% decrease.