Alcohol Abuse Health Center
Blood Alcohol
Risks
There is very little chance of a problem from having 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).
| Normal: | No alcohol is found in the blood. |
|---|---|
| Abnormal: | Any alcohol is found in the blood. |
Most states define legal intoxication as having a blood alcohol concentration (BAC) of 0.08 to 0.10 or greater. Many states define intoxication as a blood alcohol concentration (BAC) lower than 0.08 for people under age 18.
Effects of drinking alcohol
Having any amount of alcohol in the blood can cause poor judgment and slowed reflexes.
| Number of drinks per hour* | Estimated blood alcohol concentration (BAC)† | Observable effects† |
|---|---|---|
1-2 | 0.02 | Relaxation, slight body warmth |
3 | 0.05 | Sedation, slowed reaction time |
6 | 0.10 | Slurred speech, poor coordination, slowed thinking |
12 | 0.20 | Difficulty walking, double vision, nausea, vomiting |
18 | 0.30 | May pass out, tremors, memory loss, cool body temperature |
24 | 0.40 | Difficulty breathing, coma, possible death |
30 | 0.50 and greater | Death |
*1 drink = 1.5fl oz liquor (80 proof) or one glass [5fl oz] wine or one glass [12fl oz] beer. | ||
†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. | ||
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- Rubbing alcohol was used to clean the skin before inserting a needle to draw blood.
- You have high blood ketones, as in diabetic ketoacidosis.
- Taking cough medicines or herbal supplements that contain alcohol, 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
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