EtG Half-Life Calculator: Estimate How Fast Your Levels Drop
The half-life of EtG is approximately 2.5-3 hours, meaning your levels drop by about 50% every few hours after peak. This calculator uses that decay curve to project when your estimated level may fall below the 100 ng/mL or 500 ng/mL cutoff.
Editorial note
This educational page is maintained by EtGCalc and reviewed against published EtG research, SAMHSA guidance, and our calculator methodology. It does not provide medical or legal advice.
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How to Use This Calculator
Enter your sex, weight, drink count, drink type, and time since your last drink. The calculator estimates your EtG level and compares it with common 100 ng/mL and 500 ng/mL cutoffs. For a broader explanation, read our EtG calculation guide.
1What Is EtG Half-Life?
EtG half-life describes how quickly ethyl glucuronide concentration declines after it peaks. If your level is 10,000 ng/mL and the half-life is 2.5 hours, the model estimates about 5,000 ng/mL after 2.5 hours, 2,500 ng/mL after 5 hours, and so on.
Half-life is useful because EtG does not disappear in a straight line. It follows a decay curve. Early levels drop sharply, then the final low-level tail can take longer than people expect.
- Typical modeled EtG half-life: 2.5-3 hours
- Individual variation can make the curve faster or slower
- Cutoff level matters more than reaching absolute zero
2Half-Life vs Detection Window
Half-life is the rate of decline. Detection window is the time until the level falls below a lab cutoff. Those are related, but they are not the same thing.
A high starting level can require many half-lives before it drops below 500 ng/mL or 100 ng/mL. That is why the same half-life can still produce very different clearance times for light drinking versus binge drinking.
Important distinction
A short half-life does not guarantee a short detection window if the peak EtG level was very high.
3Factors That Change Your EtG Half-Life
The calculator uses a population-average decay curve. Real elimination can shift because of liver function, hydration, urine concentration, medications, body composition, and the pattern of drinking.
Use the estimate as a planning model, not a guarantee. When the stakes are high, add a safety margin instead of relying on the exact hour.
- Liver health and metabolism
- Hydration and urine concentration
- Starting peak level after drinking
- Whether the test uses 100 or 500 ng/mL
Half-Life Example Table
| Scenario | Estimate | Context |
|---|---|---|
| 0 hours after peak | 10,000 ng/mL | Starting model level |
| 2.5 hours | 5,000 ng/mL | One half-life |
| 5 hours | 2,500 ng/mL | Two half-lives |
| 10 hours | 625 ng/mL | Near the 500 cutoff |
Frequently Asked Questions
Is EtG half-life the same as detection time?
No. Half-life is the rate of decline. Detection time is when your level falls below the lab cutoff.
Can drinking water shorten EtG half-life?
Water does not make your liver metabolize EtG faster. It may affect urine concentration, but labs can flag diluted samples.
Why is my half-life longer than 3 hours?
Individual metabolism, liver function, hydration, and urine concentration can all shift real-world results.
Does EtG have a different half-life in blood vs urine?
EtG kinetics can differ by specimen type. This site focuses on urine EtG because that is the most common testing context.
How does this calculator estimate half-life?
It combines Widmark-based alcohol estimates with an exponential EtG decay model and common 100/500 ng/mL cutoffs.
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Medical & Legal Disclaimer
Not Medical Advice
EtGCalc does not provide diagnosis, treatment, or medical advice. Talk with a qualified healthcare provider about alcohol use, metabolism, testing concerns, or recovery.
Not Legal Advice
EtG testing can affect probation, custody, licensing, and employment decisions. Consult a licensed attorney or your testing program for legal questions.
If You Need Support
In the United States, SAMHSA's National Helpline is 1-800-662-4357. It is free, confidential, and available 24/7.
Calculator output is an estimate, not a test prediction. Individual metabolism, hydration, kidney function, genetics, specimen handling, and lab cutoff policy can change real results. See our methodology and sources.
References
- 1SAMHSA. The Role of Biomarkers in the Treatment of Alcohol Use Disorders, 2012 Revision.
Used for biomarker context, cutoff interpretation, and incidental exposure cautions.
- 2Jatlow et al. Ethyl glucuronide and ethyl sulfate assays in clinical trials, 2014.
Used for urinary EtG and EtS kinetics after alcohol exposure.
- 3McDonell et al. Using ethyl glucuronide in urine to detect alcohol use, 2015.
Used for EtG detection window context in clinical monitoring populations.
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