BAC – blood alcohol content or concentration – refers to the amount of alcohol in the bloodstream.
Why BAC Can Keep Rising After a Person Stops Drinking
Alcohol enters the bloodstream through the walls of the small intestine. Because alcohol dissolves in water, the bloodstream carries it throughout the body (which is 60-70%) water, where it is absorbed into body tissue high in water concentration (like the brain) and highly vascularized (meaning, lots of blood vessels – like the brain).
Alcohol is metabolized by the liver, thanks in large part to enzymes produced in the liver. This is the process by which alcohol leaves the body. The liver can only metabolize a certain amount of alcohol per hour, which means alcohol leaves the bloodstream more slowly than it enters. [This is why a person’s BAC can continue to rise after they have stopped drinking.] Because the brain controls everything we think, feel, say and do, alcohol “sitting” in the brain until the liver can metabolize it changes a person’s “thinking” and therefore their behaviors.
A very GENERAL rule of thumb is that it takes about one hour for the liver to metabolize one standard drink. A standard drink is defined as 5 ounces of table wine, 12 ounces of beer or 1.5 ounces of hard liquor. Using this very GENERAL rule of thumb, it will take two hours to metabolize two drinks — even if the drinks were consumed back-to-back, and it’s been over an hour.
BUT, no two people will necessarily metabolize alcohol in the same manner. People who weigh less, for example, have less body water as compared to someone who weighs more, and thus drink for drink a person who weighs less will have more alcohol concentration in their body water than someone who weighs more. People who have lower amounts of the liver enzymes that metabolize alcohol will take longer to metabolize the same amount of alcohol as someone else. Stage of brain development also has an influence. [See related post for more on this concept, “Underage Drinking – How Teens Become Alcoholics Before Age 21“. There are other factors that can also influence how much is “too much” for one person as compared to another.
The key message is the liver can only metabolize a certain amount of alcohol per hour. Until the alcohol is metabolized, a person still has alcohol in their bloodstream, which means their brain is still being impacted by the alcohol in their bloodstream – hence their decision-making capabilities are being impacted, as well. In this manner, a person who’s had too much to drink may actually “choose” to drink and drive or to keep drinking because “they feel fine” or engage in any number of other destructive behaviors because of the convoluted “thinking” caused by alcohol’s impact on their brain.