Blood alcohol level (BAC), is the amount of alcohol in your blood that develops from drinking beverages that contain alcohol. Levels can range from 0% (no alcohol) to over 0.4% (a potentially fatal level).
Blood alcohol content (BAC), also known as a blood alcohol level, is the amount of alcohol in your blood.
Alcohol (ethyl alcohol or ethanol) is the intoxicating ingredient found in beer, wine and liquor. When you drink a beverage that contains alcohol, your stomach and small intestines rapidly absorb the alcohol and enter it into your bloodstream. Alcohol is a toxin to your body, so your liver then metabolizes the alcohol to filter it out of your blood.
If you’re drinking faster than your liver can process the alcohol, your BAC increases and you may feel the effects of drunkenness, also called intoxication. In general, your liver can process about one alcohol-containing drink per hour. One drink is typically defined as 12 ounces of beer, 5 ounces of wine or 1.5 ounces of liquor. However, different beers and wines can contain different percentages of alcohol.
The amount of alcohol in your blood can vary based on several factors including:
Alcohol is a central nervous system depressant (it reduces stimulation in your central nervous system) and affects every organ in your body.
Here’s how different percentages of blood alcohol content (BAC) can affect you physically and mentally:
Some people can develop a tolerance to alcohol. This means that they may not feel the same physical and mental effects of alcohol drinking the same amount they used to drink. This doesn’t mean their blood alcohol content (BAC) is lower. It just means they experience the effects of alcohol differently.
People have BAC tests for a variety of reasons, including:
A healthcare provider called a phlebotomist usually performs blood draws, including those for a blood alcohol content test, but any healthcare provider who is trained in drawing blood can perform this task. A provider then sends the samples to a lab where a medical laboratory scientist prepares the samples and performs the tests on machines known as analyzers.
You can expect to experience the following during a blood test, or blood draw:
The entire procedure usually takes less than five minutes.
After a healthcare provider has collected your blood sample, they’ll send it to a laboratory for testing. Once the test results are back, the person or provider who ordered the test will share the results with you.
Blood tests are a very common and essential part of medical testing and screening. There’s very little risk to having blood tests. You may have slight tenderness or a bruise at the site of the blood draw, but this usually resolves quickly.
Depending on the reason for the BAC test, you may receive your results within a few hours to several business days.
Your report may provide blood alcohol level test results in different ways depending on the laboratory that processes the test. The results are typically reported in the percentage of blood alcohol content (BAC) — for example, 0.03% BAC. They can also be listed as grams per milliliter (g/mL). This test result would be 0.03 g/100 mL.
The results may also indicate “positive” or “negative,” meaning you did have alcohol in your blood or you had no alcohol in your blood, respectively.
The timing of a BAC test can affect the accuracy of the results. A blood alcohol test is only accurate within six to 12 hours after your last alcohol-containing drink. If you have questions or concerns about your results, talk to your healthcare provider and/or a lawyer, depending on your situation.
For most states in the United States, the alcohol limit to legally drive a vehicle for drivers aged 21 or older is currently 0.08% BAC. Utah’s legal limit is lower, at 0.05% BAC. Like all laws, these legal limits can change.
A note from Cleveland Clinic
In moderation, alcohol can be OK for people old enough to legally drink. However, if you drink excessive amounts of alcohol in a short amount of time and/or drink large amounts frequently, your health can be at risk. If you’re concerned about your drinking habits, reach out to your healthcare provider or a specialist. Together, you can come up with a plan to improve your habits and health.
Last reviewed by a Cleveland Clinic medical professional on 04/11/2022.
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