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What is an Ethyl Glucuronide (EtG) Test?
The ethyl glucuronide (EtG) test is used to detect alcohol consumption.2 EtG tests date back to 1997.6 Researchers have used them in clinical settings for decades.
An EtG tests for ethyl glucuronide, a byproduct of ethanol, which is more commonly known as drinking alcohol.
Glucuronide is a compound that the liver makes. It binds toxins and drugs in the body so you can excrete them via the urinary tract.1 In other words: When you drink alcohol, it comes out in your urine.
If you drink any amount of alcohol, EtG will form and pass through your urinary tract. Several factors play into the level of EtG that shows up in urine.
Why is an EtG Test Used?
An EtG test might be used for several reasons. Whatever the reason for administering an EtG test, it is always done to detect alcohol consumption.
A doctor might administer an EtG test on someone recovering from alcohol misuse or alcohol addiction to ensure that they are not drinking. This may be a routine part of an addiction treatment plan, alongside therapy, medication, and other resources.
Additionally, certain jobs, such as government jobs or jobs in law enforcement, may require employees to test for levels of EtG in their urine.
An EtG may also be required for the following reasons:
- As part of a liver transplant protocol
- For the school or military
- In court cases and court-mandated parenting programs
- By probation offices
However, an EtG test isn’t used if someone is suspected of drinking while working or driving. A breathalyzer is better in these situations.
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How Does an EtG Test Work? Is it Effective?
EtG test results are considered adequate for detecting alcohol consumption, though they are not necessarily specific enough.3
Higher amounts of EtG in the urine typically indicate more significant amounts of alcohol consumption.1 Other factors, such as when alcohol was consumed, also influence how much EtG is detectable. The more time that passes, the lower the EtG level is in the urine.
Some drinkers may also convert more alcohol into EtG, and others may excrete it faster.1 Drinking water may also dilute levels of EtG in urine.7
EtG can be detected even at levels below 100 ng/ml.1 Even light drinking can result in a positive EtG test.
In one study, participants were asked to report their drinking data and urine samples three times a week for 16 total weeks. The researchers then looked at low (100 ng/ml and 200 ng/ml) and moderate (500 ng/ml) EtG-I cutoffs for each. They also calculated light and heavy drinking over one to five days.
They found that EtG testing can detect 76% of light drinking for two days with a 100 ng/ml cutoff. The same cutoff detects 66% of light drinking after five days. As for heavy drinking, EtG testing can detect 84% in a day and 79% after five days.5
Another study found that EtG tests are always positive at the 100 ng/ml and 200 ng/ml cut offs within 12 hours. They become less effective at 24 hours with light alcohol use and 48 hours with heavier alcohol use.4
However, there is a maximum amount of measurable EtG. Drinking above the limit may not raise EtG levels more than can be detectable. Therefore, an EtG test effectively detects drinking, but it is not effective in detecting the amount of alcohol consumed.1
There are also some limitations to EtG tests. For example, mouthwash and hand sanitizer containing alcohol may cause EtG to be detectable in urine even with abstinence from alcohol. This causes false positives. While rare, it is possible.1
How to Interpret EtG Test Results
EtG test results are simple. A positive EtG test detects alcohol in the urine and suggests that alcohol was consumed within the last few days.
A negative EtG test would suggest that the person has not consumed alcohol within the previous few days. Keep in mind that false positives are possible.
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How Long Can EtG Be Detected in Urine?
EtG can be detected in the urine for much longer than it can be detected in the blood or in a person’s breath. In fact, it can be detectable in urine for up to 48 hours after having just a few drinks. In some cases of heavy drinking, it can be detected for up to 72 hours or more.1
It is possible to dilute levels of EtG in urine by hydrating with a lot of water and urinating often. The more time that passes, the less EtG can be detected. For example, after two days, sensitivity drops for six or less drinks.4
How Much Do You Have to Drink to Fail an EtG Test?
Because EtG is a metabolite of alcohol, EtG tests can pick up even small traces of alcohol. You may not even need to drink alcohol for EtG to show up in your urine.
Again, if you rinse your mouth with mouthwash that has alcohol in it, it is possible for it to present in an EtG test.
Will One Drink Show Up on an EtG Test?
Yes, one drink can show up on an EtG test. Other factors like how often you urinate before the test and how soon after drinking you take the test also play roles.
One drink will probably show up on an EtG test if you drank it that day. But it will likely not show up on an EtG test if you had it a few days ago.
The more alcohol you drink, the more likely it is to show up on an EtG test. Heavy drinking is more detectable than moderate alcohol consumption.
How Long Before an EtG Test Should You Stop Drinking?
An EtG test can detect alcohol within just a few days of drinking. Depending on how much alcohol you consume, an EtG test can detect it for about three days after drinking.
Alcohol abstinence for at least a few days is necessary to clear an EtG test urine sample. If you need to pass an EtG test for work, do not drink alcohol within a few days of taking the test.