BAC, or blood alcohol concentration, is a measure of the amount of alcohol in a person’s bloodstream. BAC is useful in determining what a person might feel at different levels of intoxication. If you know how to estimate and control BAC, you can avoid many of the negative consequences that occur at higher BAC levels. BAC is commonly expressed in percentage terms. For example, having a BAC of 0.08 percent means that a person has eight parts alcohol per 10,000 parts blood in the body. BAC levels can be detected by breath, blood, or urine tests.
Things That Affect BAC
Amount: How much alcohol you drink matters
Speed: Drinking fast makes your peak BAC higher
Body Size: Smaller people have higher BACs compared to larger people
Food: Alcohol gets absorbed slower with food in your stomach
Sex Differences: Females reach higher BACs faster than males because they have less water in their bodies to dilute alcohol and few enzymes that break it down
Drugs: Some drugs increase the effects of alcohol
Standard Drinks or Serving Sizes
Serving sizes or “standard drinks” are a way to standardize the amount of alcohol in a drink. Different types of alcohol have a different concentration of ethanol, the intoxicating ingredient in “alcoholic beverages.” In order to estimate someone’s intoxication level, it is important to know how much ethanol someone consumed. See below for serving sizes of the most commonly consumed types of alcohol.
12 oz Beer
8 oz Malt Liquor
5 oz Wine
1.5 oz Liquor
Effect at BACs
.02% Relaxation, loss of inhibitions
.08% Motor skills impaired, balance is affected, impaired judgments, sight and hearing affected
.10% Exaggerated emotions, lost of balance memory and judgment severely impaired
.15% All mental and physical functions impaired, blackouts, loss of control over behavior
.30% Same as surgical anesthesia, unconscious trace-like state, difficulty being roused
Binge Drinking and Blackouts
Binge drinking is drinking 5 or more drinks for males or 4 or more drinks for females within a short period of time. Binge drinking can lead to blackouts, which occur when you drink too much, too fast. Binge drinking is dangerous and could be a sign of alcoholism.
Drinking and Driving
In Virginia, if you are over 21 the legal limit for driving while intoxicated is .08 and if you are under 21it’s .02. Virginia has a zero tolerance law, which makes drinking with any alcohol amount a serious criminal offense if you are under 21.