A blood alcohol test measures the amount of
alcohol (ethanol) in your body. Alcohol is quickly absorbed into the blood and
can be measured within minutes of having an alcoholic drink. The amount of
alcohol in the blood reaches its highest level about an hour after drinking.
But food in the stomach may increase the amount of time it takes for the blood
alcohol to reach its highest level. About 90% of alcohol is broken down in the
liver . The rest of it is passed out of the body in
urine and your exhaled breath.
Alcohol has a noticeable effect on
the body, even when consumed in small amounts. In large amounts, alcohol acts
as a sedative and depresses the central nervous system.
alcohol test is often used to find out whether you are legally drunk or
intoxicated. If this test is being done for legal reasons, a consent form may
be required, but refusing to take the test may have legal consequences.
Why It Is Done
A test for blood alcohol level is done
- Check the amount of alcohol in the blood when a
person is suspected of being legally drunk (intoxicated). Symptoms of alcohol
intoxication include confusion, lack of coordination, unsteadiness that makes
it hard to stand or walk, or erratic or unsafe driving.
- Find the
cause of altered mental status, such as unclear thinking, confusion, or
- Check to see whether alcohol is present in the blood at times
when the consumption of alcohol is prohibited—for example, in underage people
suspected of drinking or in people enrolled in an alcohol treatment
How To Prepare
No special preparation is needed before
having a blood alcohol test.
Many medicines may change the results
of this test. Be sure to tell your doctor about all the nonprescription and
prescription medicines you take.
How It Is Done
The health professional drawing blood
- Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.
- Clean the needle site with a
non-alcohol solution such as povidone-iodine or antiseptic
- Put the needle into the vein. More than one needle stick may
- Attach a tube to the needle to fill it with
- Remove the band from your arm when enough blood is
- Put a gauze pad or cotton ball over the needle site as
the needle is removed.
- Put pressure on the site and then put on a
How It Feels
The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or