How BAC works
October 26, 2020
Blood alcohol concentration (BAC) is a measurement of the percentage of alcohol that's in your bloodstream after you've been drinking. Your BAC, rather than the exact amount of alcohol you've consumed, will determine the effects the alcohol will have on you. To calculate BAC, the amount of alcohol in the bloodstream is measured in milligrams (mg) of alcohol per 100 milliliters (ml) of blood. A BAC of .10% means that an individual's blood supply contains one-part alcohol for every 1000 parts blood. In the U.S .08% BAC is considered illegal to drive.
Factors that impact BAC
- Number of standard drinks
- Amount of time in which drinks are consumed
- Body weight
- Water composition
- Enzyme production and levels
- Sex assigned at birth and corresponding hormone levels
- Medications
- Food (Drunkorexia)
In general, three drinks or more will produce negative effects. These negative effects will increase the more you drink and the more quickly you drink.
Effects of alcohol at various Blood Alcohol Concentration levels
BAC Physical and Mental Effects
.01 - .03 No apparent effects. Slight mood elevation. In California, you will test as legally impaired at .01% BAC if you are under 21. It is illegal to drive or bike at this level.
.04 - .06 Feeling of relaxation. Sensation of warmth. Minor impairment of reasoning and memory.
.07 - .09 Mild impairment of balance, speech, vision and control. In California, you will test as legally impaired at .08% BAC if you are over 21. It is illegal to drive or bike at this level.
.10 - .12 Significant impairment of motor coordination and loss of judgment. Speech may be slurred.
.13 - .15 Gross impairment of motor control. Blurred vision and major loss of balance. Onset of dysphoria (anxiety, restlessness).
.16 - .20 Dysphoria predominates. Nausea may appear. Drinker has the appearance of “sloppy drunk.”
.25 - .30 Severe intoxication. Needs assistance walking. Mental confusion. Dysphoria with nausea and some vomiting.
.35 - .40 Loss of consciousness. Brink of coma.
.40 and up Onset of coma. Likelihood of death due to respiratory failure.
The blood alcohol concentration differs significantly between men and women, women tending to have higher BAC than men of the same age and weight. Moreover, men metabolize alcohol faster because they have highly active forms of an enzyme called alcohol dehydrogenase (ADH) in their stomach and their liver.
Binge drinking is the most common form of alcohol abuse in the United States. It is a serious problem on college campuses, with underage drinkers and even middle age adults. Binge drinking is defined as the consumption of 5 or more drinks for men, 4 for women, in a two-hour period. More than 15% of Americans reported binge drinking in the past 30 days, including 1 in 4 high school students (CDC, 2010).
Approximately 79,000 people die each year from alcohol-related incidents, mainly illnesses and motor vehicle accidents. Enforcing the legal blood alcohol content limit is important for public safety, but you must use caution anytime you consume alcohol, it is always best to avoid driving after you have taken a drink.
If you or someone you know has a problem with drinking, there are many resources available to help. If you are unsure consult a physician.