How Is Alcohol Detected in a Urine Test?

There are a few types of urine tests, and some are more accurate than others.

Because alcohol metabolites stay in the body long after alcohol is eliminated, tests that find metabolites will have a more extended detection period.

The urine tests for alcohol are:

• Ethanol urine test: This test measures the ethanol (alcohol) in urine. Because ethanol is eliminated through the body quickly, these tests can detect very recent use only.
• Ethyl glucuronide (EtG) urine test: EtG is an alcohol metabolite. Although EtG tests usually have a detection window of about 24 to 72 hours, the metabolite may be detected for up to 80 hours after alcohol use, especially with heavy drinking.
• Ethyl sulfate (EtS) urine test: EtS is another metabolite. EtS urine tests usually guarantee accuracy only in the first 24 hours. But much like EtG, EtS can be detected in urine about 80 hours after heavy alcohol use.

The window of detection for urine tests will vary depending on the type of test:

• Ethanol urine tests: 12 hours
• Ethyl glucuronide (EtG) urine tests: 24–72 hours
• Ethyl sulfate (EtS) urine test: 24–72 hours

If you’ve recently consumed a large amount of alcohol, the window of detection may be longer than if you had a single drink.

Although urine tests are a relatively inexpensive and noninvasive way to test for alcohol, they may be inaccurate in some cases. It’s possible to get a false positive on a urine alcohol test.

To ensure accurate results, it’s essential to:

• Make sure your hands are clean before urinating or handling a urine sample.
• If using a container, ensure that it’s clean.
• Ensure the test is sealed and hasn’t expired.
• Clean your external genitalia with a moist cloth. If you’re being tested under supervision, they will usually provide a towelette for you.

Before taking a urine alcohol test, it’s best to avoid:

• mouthwash or breath spray that contains alcohol
• “non-alcoholic” beers and wines, which may contain trace amounts of alcohol
• kombucha and fermented foods, which may contain trace amounts of alcohol
• alcohol-based sanitizer and cosmetics
• cleaning products that contain alcohol

Even if used externally and not ingested, it’s possible that products containing alcohol will cause you to test positive for alcohol consumption. It’s best to avoid anything that contains alcohol, even in tiny amounts.

Nowadays, EtG urine tests are one of the most common ways to check for alcohol consumption. They don’t only test whether you have or haven’t used alcohol — they may also indicate how much recent drinking has taken place.

For an EtG or EtS urine test:

• A high positive result (>1,000ng/mL) may indicate same-day drinking or heavy drinking on the previous day
• A low positive result (500 to 1,000ng/mL) may indicate drinking the previous day or day before, light drinking within the last 24 hours, or recent exposure to alcohol-based products
• A very low positive result (100 to 500 ng/mL) may indicate heavy drinking a few days previously, recent light drinking, or recent exposure to alcohol-based products

If you have trouble interpreting your results, consider consulting a medical professional.

If you disagree with your test results, you may be able to request a re-test from the entity that requested the test (for example, the court, your employer, or your doctor).

Urine tests are a cost-effective way to test for recent drinking.

But they do have their limitations, specifically:

• The window of detection is relatively short.
• It’s possible to dilute urine or substitute the sample with another person’s urine.
• The person being tested usually needs to be observed, which can be uncomfortable.

As with many tests, urine tests are not accurate 100% of the time. A false negative is possible. Someone may test negative for drinking alcohol when they have had alcohol recently.

EtG urine tests can detect recent drinking with a 70% accuracy — although one 2017 study showed that they’re about 85% accurate for moderate to heavy drinking.

Urine tests aren’t the only way to verify whether someone has consumed alcohol. Other methods — breath, hair, and blood tests — can detect recent alcohol consumption.

Breath tests for alcohol usually detect consumption within the past 4 to 6 hours. A Breathalyzer may measure your blood alcohol content (BAC). As such, it doesn’t test only whether you’ve had alcohol but how much you’ve had.

A hair follicle test can detect alcohol use within the past 90 days.

Blood tests can also be used to measure your BAC. Traditional tests can accurately detect alcohol consumption within the past 12 hours, and it can detect how much you’ve consumed.

There are many types of blood tests. They can also test for EtG and EtS. A carbohydrate-deficient transferrin (CDT) test can detect heavy alcohol use.

A phosphatidylethanol (PEth) blood test — a newer but highly sensitive way to test for alcohol use — measures PEth, which is formed when your body processes ethanol.

A PEth test may be able to detect alcohol consumption within the previous 1 to 3 weeks. In one 2017 study with 16 participants, PEth was detected in participants’ blood for 3 to 12 days after they had one drink. Another study noted that PEth may be detected in your blood up to 60 days after heavy, prolonged alcohol use.

Urine tests can detect alcohol or alcohol metabolites in your urine. Generally, these are accurate for 12 to 24 hours, although you may test positive up to 80 hours after drinking alcohol.

There are instances where urine alcohol tests may be inaccurate. In some cases, alternative tests — such as a breath, hair, or blood test — may be more appropriate and valuable.

Sian Ferguson is a freelance health and cannabis writer based in Cape Town, South Africa. She’s passionate about empowering readers to take care of their mental and physical health through science-based, empathetically delivered information.