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Blood Alcohol Test for Your Teen: About This Test

What is it?

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 a person has been drinking or whether someone has an alcohol-use problem.

Why is this test done?

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 alcohol is being used in an illegal way, such as in underage drinking or drinking when driving.

What happens during the test?

A health professional takes a sample of your teen's blood.

What else should you know about the test?

  • How much alcohol makes a person legally intoxicated (too drunk to drive) varies among provinces.
  • If alcohol is found in the blood, the BAC can range from very little, such as a BAC of 0.02, to a BAC of more than 0.50. A BAC of 0.50 is very high and can cause death.
  • Your blood alcohol concentration depends on many things, including your age, your size, whether you are male or female, and whether you have recently eaten. Here are some examples of BAC and its effect:
    • 0.05: Slowed reaction time
    • 0.10: Slurred speech
    • 0.20: Hard to walk, nausea, vomiting
    • 0.40: Possible coma and death

What happens after the test?

  • The doctor will give you information on how to help your teen when you get home.

When should you call for help?

Call 911 anytime you think your teen may need emergency care. For example, call if:

  • Your teen seems confused and is seeing things that are not there.
  • Your teen is thinking about suicide or about hurting others.
  • Your teen has a seizure.
  • Your teen vomits blood or what looks like coffee grounds.

Call your doctor or nurse call line now or seek immediate medical care if:

  • Your teen has trembling, restlessness, sweating, and other withdrawal symptoms that are new or that get worse.
  • Your teen's withdrawal symptoms come back after not bothering him or her for days or weeks.
  • Your teen cannot stop vomiting.

Watch closely for changes in your teen's health, and be sure to contact your doctor or nurse call line if:

  • Your teen needs help to stop drinking.

Follow-up care is a key part of your teen's treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if your teen is having problems. It's also a good idea to keep a list of the medicines your teen takes. Ask your doctor when you can expect to have the test results.

Where can you learn more?

Go to

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Care instructions adapted under license by your healthcare professional. If you have questions about a medical condition or this instruction, always ask your healthcare professional. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.