Ethanol

A blood alcohol test measures the amount of alcohol (also called ethanol) in a sample of your blood. Alcohol is the ingredient in beer, wine, and distilled spirits (liquor) that makes you feel intoxicated (drunk).

A blood alcohol test is most often used to determine not only if alcohol is present in your blood but also to what extent it's affecting you. Alcohol can change various brain functions. If you've only consumed a small amount, these changes aren't often dangerous to your immediate health. Your mood might change, and your reaction time may be reduced.