Knowra Blood alcohol concentration Blood alcohol concentration Blood alcohol concentration (BAC) is the amount of ethanol in a given volume of blood, commonly reported as a percentage or in grams per deciliter. It changes as alcohol is absorbed, distributed, and eliminated.
Alcohol absorption : The passage of ingested ethanol from the digestive tract into the bloodstream. Absorption raises BAC after drinking, with its speed affected by food and other conditions.
Driving under the influence : Operating a vehicle while impaired by alcohol or other substances, or above a legal alcohol limit. Many jurisdictions use BAC thresholds to define or prove alcohol-related driving offenses.
Blood alcohol content : A common name for the concentration of alcohol in blood, often used interchangeably with blood alcohol concentration. The word “content” can suggest a total amount, while BAC denotes concentration.
Ethanol : The alcohol in alcoholic beverages, with the chemical formula C₂H₆O. BAC specifically quantifies ethanol in blood, rather than all compounds called alcohols.
Blood-to-breath alcohol ratio : The relationship between ethanol concentration in blood and in exhaled breath. Its variation affects how accurately breath readings estimate BAC.
First-pass metabolism : Metabolism of a substance in the gut wall and liver before it reaches systemic circulation. It can remove some ethanol before absorption contributes to circulating BAC.
Field sobriety testing : Standardized roadside tasks used to assess signs of impairment, especially in suspected alcohol-impaired drivers. Observed impairment can prompt testing, but these tasks do not directly measure BAC.
Breath alcohol concentration : The concentration of ethanol in exhaled breath, measured directly by breath-testing instruments. It is a distinct measurement used to estimate, rather than directly equal, blood alcohol concentration.
Blood plasma : The liquid component of blood in which cells, proteins, and dissolved substances are suspended. Laboratory results may measure ethanol in plasma, whose concentration can differ from whole blood.
Alcohol tolerance : A reduced response to alcohol after repeated exposure, often requiring more alcohol for similar effects. Tolerance can change observed impairment without making a given BAC harmless.
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