What is a Blood Alcohol Test?

When you think of a blood alcohol test, you might picture a Breathalyzer at a traffic stop. But you might need one for other reasons, too. And there’s more than one type.

To check your blood for alcohol, your doctor uses a needle to take blood from your arm and measure the amount of alcohol. The other tests you might get for alcohol, like a breath or urine test, don’t use blood samples.

Each of these tests has the same goal: to check how much alcohol is in your body. Usually, you get a result called blood alcohol concentration (BAC). It’s a small number, like 0.05.

The higher your BAC, the more alcohol is in your system. And that affects your judgment, control, and lots of other things.

When Would I Get Tested?

You might need one for legal or medical reasons.

A legal reason can be a police officer’s suspicion that you’re driving drunk or drinking under age. It’s also common after a car crash to see if alcohol played a role. Usually, you’d take a breath alcohol test on the spot. If you refuse, you may be required to get a blood alcohol test.

You may also get one of these alcohol tests at work during random drug checks. If you have an accident on the job, your company might check whether alcohol was involved. These tests can be done with urine, blood, saliva, or breath samples.

And life insurance companies may ask for it when you apply for insurance.

Medical reasons include if you come to a hospital or the ER passed out, confused, or showing other signs of heavy drinking. It helps doctors know what’s happening and how best to care for you. Doctors often do a breath test, but sometimes will draw your blood instead.

What the Results Mean

When you have a drink, your stomach and small intestine soak it up and send the alcohol into your blood. From there, it’s your liver’s job to process it.

But your liver can only handle so much alcohol each hour. Whatever’s left over stays in your blood, so the more you drink, the higher your blood alcohol concentration.

Legal Limit for Driving

For adults 21 and over, all U.S. states have the same BAC limit: 0.08. At this point, you’re driving drunk and breaking the law.

Even if your BAC is below the legal limit, no amount of alcohol is safe when you drive. If you’re going to drink, don’t drive!

Your state may also have other laws based on your job. For example, in some states, school bus drivers need a BAC below 0.02 to be legal.

And if you’re under 21, you can’t drive with any alcohol in your blood.

Is There a “Safe” Amount to Drink?

Not if you’re driving. You might have heard the old rule of thumb that you’re fine if you’ve had at most a drink an hour because that’s what your liver can process. Don’t trust that. A lot of things affect your BAC, such as:

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