Blood Alcohol Level
Reviewed
Also called: Blood Alcohol Concentration, Ethanol Test, Ethyl Alcohol Test, Blood Alcohol Content
A blood alcohol test measures the amount of alcohol (also called ethanol) in a sample of your blood.
Specimen: Blood
Why this test may be ordered
- To check whether someone was driving after drinking alcohol
- To test for alcohol use before hiring or after a work accident
- To check for alcohol poisoning in emergency situations
- To monitor treatment for alcohol use disorder
Preparation and collection
You don't need any special preparations for a blood alcohol test.
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This process usually takes less than five minutes.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
If a result or symptoms suggest an emergency, get emergency medical help right away.
Blood alcohol level results may be given in different ways, including percentage of blood alcohol content (BAC). The effects of alcohol and your level of impairment increase as your BAC increases.
- 0.01 to 0.05% BAC: You may feel relaxed, less alert, and have a slight loss of judgement. Limitation: The timing of this test can affect the accuracy of the results. Next step: If you have questions or concerns about your results, you may want to talk to a health care provider and/or a lawyer.
- 0.06 to 0.15% BAC: You may have slurred speech, reduced muscle coordination and impaired judgement, memory or balance. Limitation: The timing of this test can affect the accuracy of the results. Next step: If you have questions or concerns about your results, you may want to talk to a health care provider and/or a lawyer.
- 0.16 to 0.30% BAC: In this range, you will feel more serious signs of intoxication such as difficulty walking and speaking. You may also feel drowsy, confused, and nauseated. You may experience gaps in memory (blackouts), vomiting or loss of consciousness. Limitation: A blood alcohol test can detect alcohol in your system for up to about 12 hours after your last drink. Next step: If you have questions or concerns about your results, you may want to talk to a health care provider and/or a lawyer.
- Over 0.31% BAC: Levels are especially dangerous and may even be fatal. You may lose consciousness, have trouble breathing, or go into a coma. Limitation: A blood alcohol test can detect alcohol in your system for up to about 12 hours after your last drink. Next step: If you have questions or concerns about your results, you may want to talk to a health care provider and/or a lawyer.
- The timing of the test can affect accuracy; it can detect alcohol for up to about 12 hours after your last drink.
- Individual factors such as weight, age, sex, type of alcohol, how quickly you drank, how much you ate, medicines you're taking, and tolerance can affect your BAC and level of impairment.
- Results may be used for legal purposes; consult a lawyer if you have legal concerns.
What to do next
If you have questions or concerns about your results, you may want to talk to a health care provider and/or a lawyer.
- What do my blood alcohol level results mean for my health and safety?
- How do factors like my weight, age, and medications affect my BAC?
- What should I do if I or someone else shows signs of alcohol poisoning?
- How can I get help if I am concerned about my alcohol use?
- What are the legal implications of my BAC results?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.