What is a blood alcohol test?
A blood alcohol test measures the amount of alcohol in the body. This measurement is called the blood alcohol concentration, or BAC.
The blood alcohol test measures only the amount of alcohol in the blood at the time the sample is taken. It does not show how long you've been drinking or whether you have an alcohol-use problem.
Why is a blood alcohol test done for teens?
A test for blood alcohol level is done to:
- Check the amount of alcohol in the blood when a person is suspected of being legally drunk.
- Find the cause of an altered state of mind, such as unclear thinking, confusion, or coma.
- See if your teen is using alcohol.
How is a blood alcohol test done?
A health professional uses a needle to take a blood sample, usually from the arm.
How do you prepare for a blood alcohol test?
In general, there’s nothing you have to do before this test, unless your doctor tells you to.
What do the results of a blood alcohol test mean?
Most states consider a person 21 or older legally drunk when the blood alcohol concentration (BAC) is 0.08 or greater. But the legal BAC limit for people under age 21 may be lower, such as 0.02.
Normal: | No alcohol is found in the blood. |
|---|---|
Abnormal: | Any alcohol is found in the blood. |
Effects of drinking alcohol
Having any amount of alcohol in the blood can cause poor judgment and slowed reflexes. BAC and the effects of drinking alcohol vary from person to person and depend upon body weight, the amount of food eaten while drinking, and each person's ability to tolerate alcohol.
Estimated blood alcohol concentration (BAC) | Observable effects |
|---|---|
| 0.02 | Relaxation, slight body warmth |
| 0.05 | Sedation, slowed reaction time |
| 0.10 | Slurred speech, poor coordination, slowed thinking |
| 0.20 | Trouble walking, double vision, nausea, vomiting |
| 0.30 | May pass out, tremors, memory loss, cool body temperature |
| 0.40 | Trouble breathing, coma, possible death |
| 0.50 and greater | Death |
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