Skip Navigation Bar
NIH MedlinePlus the Magazine, Trusted Health Information from the National Institutes of Health

Feature:
Rethinking Drinking

As Blood Alcohol Content (BAC) Increases, So Does Impairment

For purposes of law enforcement, blood alcohol content (BAC) is used to define intoxication and provides a rough measure of impairment.

Drinking glass with four levels of liquid to indicate levels of impairment: mild, moderate, severe, and life threatening

Blood Alcohol
Content (BAC)

0.0 - 0.05%

Mild Impairment – 0.0 - 0.05%

  • Mild speech, memory, attention, coordination, balance impairments
  • Perceived beneficial effects, such as relaxation
  • Sleepiness can begin
0.06 - 0.15%

Increased Impairment – 0.06 - 0.15%

  • Perceived beneficial effects of alcohol, such as relaxation, give way to increasing intoxication
  • Increased risk of aggression in some people
  • Speech, memory, attention, coordination, balance further impaired
  • Significant impairments in all driving skills
  • Increased risk of injury to self and others
  • Moderate memory impairments
0.16 - 0.30%

Severe Impairment – 0.16 - 0.30%

  • Speech, memory, coordination, attention, reaction time, balance significantly impaired
  • All driving-related skills dangerously impaired
  • Judgement and decision making dangerously impaired
  • Blackouts (amnesia)
  • Vomiting and other signs of alcohol poisoning common
  • Loss of consciousness
0.31 - 0.45%

Life Threatening – 0.31 - 0.45%

  • Loss of consciousness
  • Danger of life-threatening alcohol poisoning
  • Significant risk of death in most drinkers due to suppression of vital life functions

Spring 2014 Issue: Volume 9 Number 1 Page 23