What is a blood alcohol test?

You are probably already familiar with breathalyzer tests, which law enforcement uses to determine a person’s blood alcohol concentration (BAC). According to MedlinePlus, blood alcohol testing also determines BAC, and these tests are often considered more accurate.

Understanding how and why law enforcement uses these tests ensures you are aware of your rights. Here are a few key points to keep in mind.

Why law enforcement uses blood tests

The breathalyzer is usually the first test administered when law enforcement suspects a person is driving under the influence. You can request a blood alcohol test instead if you prefer it to the breathalyzer. Law enforcement can also require one to follow up the breathalyzer or request a blood alcohol test if you refuse the breathalyzer.

What to expect during testing

A health care worker will draw a small amount of blood from your arm using a needle, which is then taken and tested to assess BAC. It is similar to other types of blood tests and is usually completed within five minutes or less. While there is a light pinch, most people do not experience significant discomfort.

How to interpret results

A person with no alcohol in their system should measure a 0.0% BAC. As for the legal limit, drivers measuring .08% or higher can receive DWI. Significant inebriation occurs between .08% and .40%, including tiredness, problems walking, and slurred speech. Having a BAC higher than .40% incurs a risk of illness or even death due to alcohol poisoning.

The longer you wait to administer a test, the more its accuracy diminishes. For example, if law enforcement conducts a test from six to 12 hours after your last drink, it will affect the results.