Version July 2025
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What is a blood ethanol concentration? —
This is a test to measure the amount of ethanol in the blood. It is sometimes called blood alcohol concentration, or "BAC."
Ethanol, or "ethyl alcohol," is a type of alcohol. There are many different alcohols, but ethanol is the type in alcoholic drinks.
When you drink alcohol (including beer, wine, or liquor), it gets into your bloodstream. As the blood ethanol concentration increases, it can cause signs of being drunk, like trouble with balance or not thinking clearly. At high concentrations, it can cause serious health problems.
There is also a breath test that can measure a person's ethanol concentration.
Why might I get a blood ethanol concentration? —
This test might be done:
●To confirm that alcohol poisoning is the cause of symptoms such as confusion
●Along with other tests if a person was in a serious accident
How is this test done? —
You need to get a "blood draw." For a blood draw, a needle is used to take a small amount of blood from your arm (figure 1). Collecting the blood only takes a few minutes. The blood is then tested in a lab.
Most of the time, getting blood taken does not cause problems. You might have a little soreness or bruising where the needle went in.
What do my results mean? —
Blood ethanol is usually reported as a number that tells you the concentration.
A result of 0 mg/dL (0 mmol/L) means there is no ethanol in the blood.
As the blood ethanol concentration increases, it can cause symptoms:
●20 to 100 mg/dL (4 to 22 mmol/L) – A person can start having mild trouble with coordination, attention, and thinking. In most US states, 0.08% or 94 mg/dL (20 mmol/L) is the legal limit for driving.
●100 to 200 mg/dL (22 to 43 mmol/L) – A person has more trouble with coordination and control. Their speech, judgment, and mood can be affected.
●200 to 300 mg/dL (43 to 65 mmol/L) – A person can have trouble walking, confusion, nausea, and vomiting. They often seem "drunk."
●300 mg/dL (65 mmol/L) or higher – A person might pass out or be unable to respond normally. In some cases, these concentrations can cause breathing problems, coma, and even death.
The test result might not always reflect symptoms in this way. For example, a person who drinks alcohol regularly might not seem drunk, even if their blood ethanol concentration is high.
Patient education: Alcohol poisoning (The Basics)
Patient education: Alcohol and your health (The Basics)
Patient education: Alcohol use – When is drinking a problem? (The Basics)
Patient education: Substance use disorder (The Basics)
Patient education: Risks and benefits of alcohol (Beyond the Basics)
Patient education: Alcohol use — when is drinking a problem? (Beyond the Basics)
