Alcohol is one of the most widely abused substances but also one of the most difficult to monitor. Fortunately, two sensitive and specific biomarkers facilitate monitoring alcohol use. Ethyl glucuronide (EtG) and ethyl sulfate (EtS) are minor ethanol metabolites produced by the liver. They are direct biomarkers of ethanol exposure. EtG and EtS are highly sensitive, water soluble, nonvolatile metabolites that can be detected at quantifiable levels in hair, urine, oral fluid, and blood. Urine, however, is the preferred matrix for testing.

What is ethyl glucuronide? Ethyl glucuronide (EtG) is a direct metabolite of ethyl alcohol (ethanol). Its presence in urine can be used to detect recent alcohol exposure, even after ethanol is no longer measurable.

What is ethyl sulfate? Ethyl sulfate (EtS) is a specific metabolite of ethanol that is stable in urine and not subject to degradation or post-collection formation.

What is the detection window for EtG/EtS testing? The presence of EtG/EtS can reveal very small acute doses, chronic alcohol consumption, and anything in between, from as soon as two hours and up to 80 hours post-consumption at industry-standard cutoffs, depending on the amount used and the frequency of use. Parent alcohol testing is limited to approximately 8–12 hours post-consumption.

How reliable is EtG/EtS testing? The presence of both EtG and EtS in body fluids indicates exposure to ethyl alcohol and cannot come from exposure to other types of alcohol, such as isopropyl alcohol. Incidental exposure (from ethanol-based medication, hand sanitizers, food sources, mouthwash, etc.) could result in low-level positives for EtG, EtS, or ethanol. Patients should be provided with a list of potential sources of ethanol exposure. Excessive use of hand sanitizers (for instance, by health professionals) may cause EtG levels only to exceed 500 ng/mL.

Can EtG results tell me how much alcohol has been consumed? Any positive result means the liver has processed alcohol (ethanol). EtG/EtS production may vary among individuals, and because of the long detection period, estimating the amount of alcohol consumed is not possible. In general, the greater the ng/mL value, the more recent and/or heavy the consumption has been.

How stable is EtG/EtS in a urine specimen? EtG/EtS is stable in a urine specimen for at least seven days at room temperature, one month when refrigerated, and up to 12 months when frozen. In certain rare scenarios, EtG can form post-collection. For example, if a person with uncontrolled diabetes has excess glucose in their urine and a urinary tract infection, the sample could be exposed to bacteria such as E. coli, and EtG can be formed in vitro. EtS is not prone to this same phenomenon. Certain bacteria, such as E. coli, can degrade EtG but not EtS.