blodalkoholkoncentration

Blodalkoholkoncentration (BAC) refers to the amount of ethanol in the bloodstream. It is usually expressed as grams of ethanol per liter of blood (g/L) or as a percentage of blood volume (g per 100 milliliters). In many Nordic countries, BAC is reported in promille (‰), where 1‰ corresponds to one gram of ethanol per liter of blood. BAC is a key indicator in clinical toxicology, forensic science, and traffic safety.

Measurement can be done directly by analyzing a blood sample or indirectly with breath, urine, or saliva tests. Blood tests are more accurate, while breath tests are commonly used in roadside and workplace settings. Breath analysers estimate BAC by relating the amount of alcohol in a breath to blood using a fixed ratio.

Legal limits for driving and operating heavy machinery vary by country and sometimes by age or licensing status. A typical value in many European countries is 0.5‰, while the United States uses 0.08% BAC. Some jurisdictions have stricter limits for young or professional drivers, and some apply zero tolerance.

Alcohol is absorbed from the stomach and small intestine and metabolized mainly in the liver at an average rate of about 0.015 g/dL per hour (roughly 0.15 g/L per hour). Peak BAC occurs after a peak absorption period and depends on dose, drinking speed, and food in the stomach. Individual factors such as sex, body weight, genetics, and medications influence BAC and its effects.

BAC levels correlate with impairment and risk of accidents, but effects vary with tolerance and other factors. BAC testing plays a central role in clinical care, law enforcement, and public safety.