The EtG test can detect alcohol in urine up to 3 days or longer after heavy alcohol consumption. If only a few drinks were ingested, then this test can detect alcohol in urine for up to 2 days, according to the Medical University of South Carolina's Institute of Psychiatry. The EtG test or ethyl glucuronide test can detect the presence of even very small levels of ethanol.
The test works because alcohol and glucuronic acid are produced in the liver. This compound is excreted in urine when glucuronic acid binds with ethyl alcohol (ethanol), as stated by NMS Labs.
A disadvantage of this test can be that incidental alcohol exposure, such as alcohol found in foods, mouthwashes, cough medications and vanilla extract, can be detected and can produce a false positive, as noted by Drug Testing Network Inc.