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Blood Alcohol

Risks

There is very little chance of a problem from having a blood sample taken from a vein.

  • You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
  • In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
  • Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

Results

A blood alcohol test measures the amount of alcohol (ethanol) in your body. Some states have no set limit for legal intoxication. But the National Highway Traffic Safety Administration (NHTSA) recommends that all states set the legal definition of intoxication as the point when the blood alcohol concentration (BAC) exceeds 0.08 (which is equivalent to 80 mg/dL or 17 mmol/L).

Blood alcohol
Normal:

No alcohol is found in the blood.

Abnormal:

Any alcohol is found in the blood.

Legal intoxication is defined as having a blood alcohol concentration (BAC) of 0.08 or greater. But the legal blood alcohol concentration (BAC) limit for people under age 18 may be lower, such as 0.02.

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.

Effects of drinking 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

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Using rubbing alcohol to clean the skin before inserting a needle to draw blood.
  • You have high blood ketones, as in diabetic ketoacidosis.
  • Taking cough medicines that contain alcohol or herbal supplements, such as kava or ginseng.
  • Drinking other alcohols, such as isopropyl alcohol or methanol.

Many medicines may change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take.

WebMD Medical Reference from Healthwise

Last Updated: November 07, 2011
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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