What is BAC (Blood Alcohol Concentration)?

Your blood alcohol concentration (BAC) is the ratio of alcohol to blood in your body.

Some facts regarding Blood Alcohol Concentration (BAC):

  • If your BAC is 0.08%, you have eight units of alcohol for every 10,000 units of blood in your bloodstream.
  • A person with a BAC level of .08 or higher loses his/her muscle coordination and control and ability to think, judge, concentrate and react, and is considered an impaired driver.
  • For drivers 21 and older, it is illegal to drive with the BAC level of .08 and higher.
  • The BAC level limit for drivers under 21 is 0.01. But remember, drinking under the age of 21 is illegal. You can easily reach 0.01 alcohol level by drinking one 12-oz. beer.

    This law of 0.01 alcohol level is created, so if you need to take a cough medicine which may contain alcohol, you can only drive as long as your BAC level stays below the 0.01 limit.

What is "one drink"?
It depends on the kind of alcohol you are considering. A standard drink contains approximately four grams of alcohol, which is equal to about 0.6 fluid ounces, or 1.2 tablespoons.

Examples of "one drink":

  • One 12-oz. beer
  • One 5oz. glass of wine
  • One 1.5-oz. shot of hard liquor

Each one of the above example of "one drink" would raise your BAC level the same amount. One drink will not raise everyone's BAC in the same way.

Effects and levels of alcohol in the body depend on the factors below:

A person's size and weight.
It takes less alcohol consumption and a shorter time for a lighter and smaller person to become impaired and drunk than a heavier, larger person.

(The below examples are just an estimation. There are other factors other than weight that can affect one's impairment; this should not be used as a reference for deciding whether a person should drive after drinking. I would recommend not driving even after one drink – this is because drinking causes fatigue, loss of focus, impaired judgment and reduces reaction time to hazards.)

  • A 120-lb. person may become impaired after about two drinks and considered legally drunk after about three drinks.
  • A 160-lb. person can become impaired after about three drinks and considered legally drunk after about four drinks.
  • A 200-lb. person can become impaired after about four drinks and considered legally drunk after about five drinks.
  • How fast a person consumes alcohol. The body needs time to break down the alcohol and deliver it to the brain. If a person drinks faster, the absorption of the alcohol into the bloodstream is quicker and he/she will have a higher BAC level. If a person drinks slower, the absorption of the alcohol into the bloodstream is slower and he/she will have a lower BAC level.
  • Gender differences. Women's bodies do not break alcohol down as fast as men's. Women possess less dehydrogenase, an enzyme in the body responsible for breaking down alcohol. Women are also smaller, on average, which means their BAC will rise more easily.

Other important factors that cause different alcohol effects on your body:

  1. Whether the alcohol is taken on an empty stomach or full stomach.
  2. Individual metabolism rate.
  3. The amount and type of food that a person takes with the alcohol.
  4. The concentration of the alcohol beverage.

What are alcohol's effects at different BAC levels?

.01% - .03% BAC

  • Less sound judgment and lower awareness
  • Mild relaxation
  • Altered mood
  • Impaired visual functions (e.g., a declined ability to track a moving target)
  • Significantly reduced ability to multi-task and have divided attention

.03% - .50% BAC

  • Considerably weakened judgment and awareness
  • Substantially affected mood and behavior
  • Loss of the ability to control small-muscle such as the ability to focus
  • Declined hand-eye coordination
  • Declined ability to steer effectively
  • Declined ability to track moving objects
  • Reduced ability to react effectively to driving situations

.05% - .80% BAC

  • Impaired muscle coordination including balance, vision, and hearing
  • Significantly declined ability to react effectively to driving situations
  • Significantly reduced ability to stay alert, stay focused, and notice a driving hazard or situation
  • Significantly impaired ability to think clearly and effectively
  • Significantly reduced ability to concentrate and multitask
  • Short-term memory loss, which causes drivers to forget to follow basic traffic rules
  • Impaired perception of speed
  • Impaired depth perception and the ability to judge distance
  • Reduced information processing capability such as visual search and detecting signals

.08% - .10% BAC

  • Substantially impaired muscle coordination and control
  • Substantially impaired ability to think, judge, concentrate and react
  • Impaired and dangerous driving
  • Impaired ability to maintain lane position
  • Impaired ability to change lanes, respond or react to a traffic situation or brake effectively
  • Significantly reduced ability to stay awake, aware and alert
  • Impaired ability to follow traffic laws and be careful near pedestrians and children

.10% - .15% BAC

  • Almost fully impaired muscle coordination and control
  • Almost fully impaired ability to think, judge, concentrate and react
  • Almost fully impaired ability to balance
  • Possibility of vomiting
  • Almost fully impaired and dangerous driving

.15% - .20% BAC

  • Fully impaired muscle coordination, control, and balance
  • Impaired ability to walk or stand
  • Confusion and disorientation
  • Nausea and vomiting
  • Impaired reflexes are impaired including gag reflex, which can cause suffocation if vomiting occurs
  • Very dangerous driving

.20% - .25% BAC

  • Fully impaired physical, mental, and sensory functions
  • Extremely dangerous state of being with a risk of asphyxiation from suffocating on vomit

.25% - .30% BAC

  • Risk of death
  • Stupor or comatose state
  • Little comprehension of the situation
  • May suddenly pass out, and difficulty waking up

.30% - .40% BAC

  • Risk of death.
  • Possible coma or not breathing

.40%+ BAC

  • Risk of death - chances of survival are significantly reduced
  • Coma
  • Impaired respiratory function
  • Erratic heartbeat