What does Blood Alcohol Concentration (BAC) measure?

What does Blood Alcohol Concentration (BAC) measure?

• A. The concentration of alcohol in the blood, directly proportional to the concentration in the brain.
• B. The percentage of alcohol absorbed in the stomach.
• C. The total volume of blood in a sample.
• D. The rate at which the liver metabolizes alcohol.

Answer: (A)

BAC measures the amount of ethanol present in the bloodstream, and because ethanol distributes through body water and quickly crosses into the brain, the blood level tends to reflect how much ethanol is reaching brain tissue. This is why a higher BAC generally corresponds to greater impairment—the brain is exposed to more alcohol as blood levels rise. It’s not a measure of how much alcohol was absorbed in the stomach, nor a measure of total blood volume, nor the rate at which the liver metabolizes alcohol. Keep in mind the brain concentration is related to blood concentration, with some individual variation and timing effects, but BAC serves as a practical proxy for brain exposure and intoxication.

BAC measures the amount of ethanol present in the bloodstream, and because ethanol distributes through body water and quickly crosses into the brain, the blood level tends to reflect how much ethanol is reaching brain tissue. This is why a higher BAC generally corresponds to greater impairment—the brain is exposed to more alcohol as blood levels rise. It’s not a measure of how much alcohol was absorbed in the stomach, nor a measure of total blood volume, nor the rate at which the liver metabolizes alcohol. Keep in mind the brain concentration is related to blood concentration, with some individual variation and timing effects, but BAC serves as a practical proxy for brain exposure and intoxication.