What is blood alcohol concentration (BAC)?

• A. The rate at which alcohol is metabolized.
• B. A measure of the brain's electrical activity after drinking.
• C. The amount of alcohol in the blood, expressed as a percentage.
• D. The volume of alcohol in a single drink.

Answer: (C)

Blood alcohol concentration (BAC) is the amount of ethanol in the bloodstream, expressed as a percentage. It isn’t about how fast the body is breaking down alcohol, nor a measure of brain electrical activity, nor the volume of alcohol in one drink. Instead, BAC reflects the concentration of alcohol in the blood at a given moment and is typically determined by a blood test or breathalyzer, expressed as a percentage (for example, 0.08%) or sometimes in mg/dL. Factors like how much and how quickly you drank, your body weight and composition, sex, whether you’ve eaten, and your metabolism all influence BAC. Understanding BAC helps explain how impairment relates to legal limits and safety considerations.