EtG vs EtS: Understanding Different Alcohol Biomarkers
While EtG is the most common alcohol biomarker, EtS (Ethyl Sulfate) is often tested alongside it. Here's why both matter for accurate alcohol detection.
Quick Summary
EtG (Ethyl Glucuronide) and EtS (Ethyl Sulfate) are both direct metabolites of alcohol. Testing both together increases detection accuracy and helps distinguish genuine alcohol consumption from incidental exposure.
What Are EtG and EtS?
Ethyl Glucuronide (EtG)
EtG is formed when ethanol binds with glucuronic acid through a process called glucuronidation, catalyzed by the UDP-glucuronosyltransferase (UGT) enzyme family in the liver.
Chemical Formula: C₈H₁₄O₇
Molecular Weight: 222.19 g/mol
Production Rate: Approximately 0.5-1.5% of consumed ethanol
Ethyl Sulfate (EtS)
EtS is produced when ethanol undergoes sulfation, a phase II metabolic reaction catalyzed by sulfotransferase (SULT) enzymes, also primarily in the liver.
Chemical Formula: C₂H₆O₄S
Molecular Weight: 126.13 g/mol
Production Rate: Approximately 0.1-0.4% of consumed ethanol (lower than EtG)
Key Differences Between EtG and EtS
| Characteristic | EtG | EtS |
|---|---|---|
| Metabolic Pathway | Glucuronidation | Sulfation |
| Concentration in Urine | Higher (3-5x more than EtS) | Lower |
| Detection Window | 24-80+ hours | Similar to EtG |
| Stability in Urine | Can degrade if sample not stored properly | More stable than EtG |
| Bacterial Degradation | Susceptible to E. coli degradation | Resistant to bacterial breakdown |
| Cost to Test | More affordable | Slightly more expensive |
| Incidental Exposure | Can detect from hand sanitizer, mouthwash | Also detects incidental exposure |
Why Test Both EtG and EtS Together?
1. Increased Accuracy
Testing both biomarkers simultaneously provides higher confidence in results. If both are positive, it strongly confirms alcohol consumption. If only one is positive, it may warrant further investigation.
2. Protection Against Sample Degradation
EtG can break down if urine samples aren't refrigerated or if bacterial contamination occurs (especially E. coli). EtS is more resistant to degradation, so if EtG is low but EtS is present, it suggests the sample may have degraded rather than representing a false positive.
3. Confirmation of Genuine Consumption
The presence of both EtG and EtS in the correct ratio (typically EtG/EtS ratio of 3:1 to 5:1) strongly indicates genuine beverage alcohol consumption rather than incidental environmental exposure.
4. Reduced False Positives
Using both markers together helps distinguish between significant alcohol use and trace exposures from sources like hand sanitizer, perfume, or mouthwash, which may produce low levels of one marker but not necessarily both in the expected ratio.
The EtG/EtS Ratio
The ratio between EtG and EtS levels provides additional diagnostic value:
Forensic toxicologists and medical review officers use this ratio as one factor among many when interpreting test results, especially in cases where the result has legal or professional consequences.
Which Test Should You Expect?
The type of test you receive depends on the testing organization and purpose:
EtG Only Tests
- •Lower cost option
- •Common for routine monitoring
- •Workplace screening
- •Initial probation testing
EtG + EtS Combined Tests
- •Legal proceedings
- •Child custody cases
- •Professional licensing boards
- •Medical abstinence programs
The Bottom Line
While EtG remains the primary alcohol biomarker used in most testing scenarios, the combination of EtG and EtS provides a more robust and reliable method for detecting alcohol use.
EtS serves as a valuable confirmatory marker that enhances test accuracy, protects against false positives from sample degradation, and helps distinguish genuine consumption from incidental exposure.
If you're subject to alcohol testing, understanding both markers—and how they work together—gives you a more complete picture of what your test results actually mean.
Calculate Your EtG Levels
While our calculator focuses on EtG (the more commonly tested marker), understanding both biomarkers helps you interpret your results more accurately.
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