Blood alcohol concentration is defined as the percentage of alcohol (ethyl alcohol or ethanol) in a person's bloodstream. A BAC of 0.05% means there are 0.05 grams of alcohol in 100 ml of blood.

When talking about measuring alcohol concentration, people often think of alcohol concentration measuring devices using a blower. However, measuring alcohol concentration in the blood has more accurate results than breathing. So when is it done and what does the blood alcohol concentration measurement result mean?