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What Is BAC?: Effects on the Brain and Body

What Is BAC? | Effects on the Brain and Body | Just Believe Recovery PA

In This Article

BAC, or blood alcohol concentration, is a measurement of the percentage of alcohol in a person’s bloodstream after they have been drinking. BAC, rather than the precise amount of alcohol that has been consumed, will determine the effects the alcohol will have on an individual.

In all states, the legal driving limit is 0.08% BAC. Nonetheless, a person may still be arrested if their BAC is below this limit if they are exhibiting signs of impaired driving. This may occur due to the individual having an extremely low tolerance for alcohol or the presence of other substances in the system that can compound the effects of alcohol or directly from the independent effects of that particular medication or drug.

Factors That Affect BAC

  • Height
  • Weight
  • Sex
  • Overall physical condition
  • Other drugs in body
  • Food contents in stomach
  • Amount of sleep
  • Alcohol content of drinks

As BAC increases, the level of alcohol-related impairments a person may experience increases. While a breathalyzer gives rapid results and is often used by law enforcement who suspect a person has been driving while impaired, it is not as accurate as measuring BAC using a blood test.

How BAC Is Calculated

The alcohol level in the bloodstream is measured in milligrams of alcohol per 100 milliliters of blood when calculated. It is typically expressed as a decimal, such as 0.08.

For example, a BAC of 0.10% indicates that a person’s blood contains one part alcohol for every 1,000 parts of blood.

What Is a Standard Drink?

A standard drink is equivalent to 14 gm (0.6 oz.) of pure alcohol. In general, this amount of pure alcohol is found in the following:

  • 12 oz of beer or hard seltzer (4-5% alcohol content)
  • 8 oz of malt liquor (7% alcohol content)
  • 5 oz of wine (12-14% alcohol content)
  • 1.5 oz of 80-proof (40% alcohol content) liquor or distilled spirits or liquor (e.g., gin, rum, vodka, whiskey)

How BAC Affects Impairment

What Is BAC? | Effects on the Brain and Body | Just Believe Recovery PA

The Centers for Disease Control and Prevention (CDC) provides the following information that describes how alcohol consumption and BAC can affect judgment, behavior, physiology, and driving ability.


Some loss of judgment, feelings of relaxation, slight body warmth, altered mood

Reduced visual function and ability to perform two tasks simultaneously


Exaggerated behavior, mild loss of small-muscle control (e.g., eye focus), impaired judgment, lowered alertness, the release of inhibition

Mildly impaired coordination reduced ability to track moving objects, difficulty steering, reduced response to emergency driving situations


Poor muscle coordination (e.g., balance, hearing, reaction time, speech, vision), difficulty identifying potential danger, impaired judgment, self-control, reasoning, and memory

Loss of concentration and short-term memory, impaired speed control, reduced information processing capability such as signal detection and visual search, impaired perception


Apparent deterioration of reaction time and control, slurred speech, significantly impaired coordination, slowed thinking

Decreased ability to maintain lane position and brake as needed

0.15% and Above

Far less muscle control than usual, the potential for vomiting, possibly profound loss of balance

Substantial impairments in vehicle control, attention to driving task, and visual and auditory processing

Note: Many reports of persons with a significant tolerance for alcohol and high BAC levels may exhibit minimal behavioral deficits on simple observation due to the tolerance that develops with chronic use.

BAC Test Results

If a person is subject to BAC testing, such as via breathalyzer or a urine or blood screen, typical interpretation of the result look something like this:

  • Sober: 0.00% BAC
  • Legally intoxicated: 0.08% BAC
  • Very impaired: 0.08–0.40% BAC
  • At the risk of severe complications including coma and death: Above 0.40% BAC

Getting Treatment for Alcohol Abuse and Addiction

Persons who regularly abuse alcohol, especially if they have been drinking and driving (whether or not they have ever been arrested), are urged to seek professional treatment as soon as possible.

Alcoholism is a potentially devastating and even life-threatening condition that should be approached as a multi-causal disorder with many contributing emotional factors, including comorbid mental health conditions, such as depression, anxiety, and the experience of trauma.

Just Believe Recovery is a specialized addiction treatment center that offers comprehensive, individualized programs in both inpatient and intensive outpatient treatment formats. We aim to ensure each individual we treat receives the most effective care and support and all the tools they need to reclaim their lives and foster long-lasting sobriety and wellness.

We Believe Recovery Is Possible For Everyone.
If you or a loved one needs help with substance abuse and/or treatment, please contact Just Believe Recovery PA at (888) 380-0342. Our specialists can assess your needs and help you get the treatment that provides the best chance for your long-term recovery.
Just Believe Recovery Carbondale

Just Believe Recovery is a fully licensed, Joint Commission accredited, comprehensive drug and alcohol treatment center located in Carbondale, Pennsylvania

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