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Christoph Law Offices, DUI & Criminal Defense
Christoph Law Offices, DUI & Criminal Defense


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  • Former Deputy San Diego City Attorney
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Attorneys William R. Christoph & Nicholas W. Christoph

Understanding Blood Alcohol Levels for DUI

by | Apr 20, 2024

Driving under the influence (DUI) is a serious offense with potentially severe consequences, and one of the primary factors in determining DUI is the blood alcohol concentration (BAC) level of the driver. BAC refers to the percentage of alcohol in a person’s bloodstream. In the United States, each state has its own laws and regulations regarding DUI and BAC limits, but there are some general guidelines and trends that apply nationwide.

What is Blood Alcohol Concentration (BAC)?

BAC is a measure of the amount of alcohol present in a person’s bloodstream. It is typically expressed as a percentage. For example, a BAC of 0.10% means that one-tenth of a percent of a person’s blood is alcohol. BAC is influenced by factors such as the number of drinks consumed, the rate of consumption, body weight, gender, metabolism, and the presence of food in the stomach.

Legal BAC Limits for DUI

In the United States, the legal BAC limit for driving is set by individual states. However, the limit is typically 0.08% for drivers aged 21 and over. This means that if a driver’s BAC is 0.08% or higher, they are considered legally under the influence and can be charged with DUI.  In California, while it is illegal to drive with a .08 BAC or more.  The NTSB (National Transportation Safety Board) recommends lowering the BAC level to .05.  In California, you can be charged with a DUI at .05 BAC or more based on factors showing impairment at that level.

For drivers under the age of 21, many states have zero-tolerance laws, meaning that any detectable amount of alcohol in the bloodstream can result in DUI charges. Additionally, commercial drivers, such as truck drivers, are often subject to lower BAC limits, typically around 0.04%.

Effects of Different BAC Levels

Understanding the effects of different BAC levels is crucial for recognizing when it is unsafe to operate a vehicle. Here’s a general overview of how BAC levels correlate with impairment:

  • 0.02% – 0.03% BAC: Some loss of judgment, relaxation, slight body warmth, altered mood.
  • 0.05% – 0.07% BAC: Reduced coordination, impaired judgment, lowered inhibitions, difficulty tracking moving objects.
  • 0.08% – 0.10% BAC: Significant impairment of motor coordination and judgment, slowed reaction time, difficulty controlling speed, impaired perception.
  • 0.10% – 0.15% BAC: Substantial impairment, slurred speech, blurred vision, difficulty maintaining balance.
  • 0.15%+ BAC: Severe impairment, increased risk of accidents, potential for blackouts, vomiting, loss of consciousness.

Consequences of DUI

The consequences of a DUI conviction can be severe and can vary depending on factors such as BAC level, prior offenses, and whether anyone was injured as a result of the impaired driving. Some common consequences of DUI convictions can  include:

  • Fines and court costs
  • License suspension or revocation
  • Mandatory alcohol education or treatment programs
  • Community service
  • Probation
  • Installation of an ignition interlock device (IID)
  • Jail time

Additionally, a DUI conviction can have long-term consequences such as increased insurance premiums, difficulty obtaining employment, and a permanent criminal record.Driving under the influence of alcohol is a serious offense that can have far-reaching consequences for both the driver and others on the road. Understanding blood alcohol concentration (BAC) levels and their effects is essential for making responsible decisions about alcohol consumption and driving. Remember, if you plan to drink, designate a sober driver, use public transportation, or arrange for a ride-sharing service to ensure everyone’s safety on the road.



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