In a person with normal intestinal anatomy, blood alcohol content (BAC) and alcohol metabolism are a function of three things:
Consumption: The amount of alcohol consumed will ultimately control the upper range of an individual’s peak BAC. An alcoholic beverage can raise the BAC by 0.02 to 0.025 per 1 unit of alcohol (i.e., a 12 oz beer or 1.5 oz. 80-proof liquor beverage) consumed.
Distribution: The stomach acts as the gatekeeper; if there is food in the stomach, the food-filled stomach will slow down the emptying of its contents into the small intestine. The small intestine has a very rich blood supply. That results in those blood vessels bringing the alcohol from the inside of the intestine directly into the bloodstream.
Elimination: Twenty percent of alcohol absorption occurs in the stomach because of the enzyme alcohol dehydrogenase. The partially processed alcohol then enters the small intestine and then the bloodstream. From there, it is transported via the portal circulation to the liver for additional processing. The remaining 80% of the elimination of alcohol occurs in the liver by alcohol dehydrogenase. Elimination occurs at a fixed amount per hour, regardless of age, weight, or gender.