Blood Alcohol Level

A blood alcohol test measures the amount of alcohol (also called ethanol) in a sample of your blood. Alcohol is the ingredient in beer, wine, and distilled spirits (liquor) that makes you feel intoxicated (drunk). When you have an alcoholic drink, your digestive tract quickly absorbs the alcohol.

It then enters your bloodstream and stays there until your liver can break it down and filter it out of your blood. Your liver needs time to do this. If you consume alcohol faster than your liver can get rid of it, your blood alcohol levels will rise.

The higher these levels rise, the more intoxicated you'll feel. There are a few blood tests that can measure whether a person has been drinking alcohol. The most common is the blood alcohol concentration/content (BAC) test.

This test shows the amount of alcohol in your blood for up to 12 hours after drinking. Other blood tests measure substances that may stay in your blood for weeks after you've had alcohol. These tests are typically used to test for alcohol use disorder (AUD) or to check whether a person recovering from AUD has stayed sober.

Why this test is done

You may need a blood alcohol test if you are suspected of drunk driving and/or have symptoms of intoxication. These include:

• Difficulty with balance and coordination.
• Slurred speech.
• Slowed reflexes.
• Nausea and vomiting.
• Mood changes.
• Poor judgment.

You or your child may also need this test if there are symptoms of alcohol poisoning. In addition to the above symptoms, alcohol poisoning can cause:

• Confusion.
• Irregular breathing.
• Seizures.
• Low body temperature.

How to prepare

You don't need any special preparations for a blood alcohol test.

Sample type

Blood

Other names for this test

blood alcohol level test, ethanol test, ethyl alcohol, blood alcohol content