The EtG Formula Explained
A deep dive into Ethyl Glucuronide: molecular structure, the glucuronidation process, and how your liver breaks down alcohol into detectable metabolites.
What is Ethyl Glucuronide (EtG)?
Ethyl Glucuronide (EtG) is a direct metabolite of ethanol (drinking alcohol). It's formed when your liver processes alcohol through a process called glucuronidation.
Molecular Formula
Molecular Weight: 222.19 g/mol
Key Properties
- Water-soluble compound
- Non-volatile (won't evaporate)
- Stable in urine samples
- Detectable for 24-80 hours
Why It's Used for Testing
- Direct biomarker of alcohol
- Long detection window
- Highly specific to ethanol
- Can't be produced by fermentation
The Glucuronidation Process
Glucuronidation is your liver's way of making substances water-soluble so they can be excreted in urine. Here's how alcohol becomes EtG:
Alcohol Enters the Liver
After drinking, ethanol (C2H5OH) is absorbed into your bloodstream and transported to the liver for processing.
UDP-Glucuronosyltransferase (UGT) Enzyme Acts
The UGT enzyme family (specifically UGT1A1 and UGT2B7) catalyzes the attachment of glucuronic acid to ethanol.
EtG is Formed
The chemical reaction produces Ethyl Glucuronide, a water-soluble compound that can be filtered by the kidneys and excreted in urine.
Excretion in Urine
EtG is filtered by the kidneys and concentrated in urine, where it can be detected by laboratory testing for up to 80 hours after heavy drinking.
The Chemical Reaction
The EtG Calculation Formula
Our calculator uses a multi-step formula to estimate EtG levels:
Step 1: Calculate Peak BAC (Widmark Formula)
Step 2: Estimate Peak EtG
(Approximately 3,500 ng/mL per 0.01% BAC)
Step 3: Apply Decay Function
Half-life of approximately 2.5-3 hours
Widmark Factor (r)
EtG vs Other Alcohol Metabolites
| Metabolite | Detection Window | Sample Type |
|---|---|---|
| EtG (Ethyl Glucuronide) | 24-80 hours | Urine, Hair |
| EtS (Ethyl Sulfate) | 24-48 hours | Urine |
| PEth (Phosphatidylethanol) | 2-4 weeks | Blood |
| FAEE (Fatty Acid Ethyl Esters) | Up to 6 months | Hair |
EtG is the most commonly used biomarker for recent alcohol use due to its balance of detection window length and test accessibility.
EtG Half-Life & Decay Rate
Half-Life
This means EtG concentration drops by 50% every 2.5-3 hours after peak levels are reached.
Example Decay
- Peak: 10,000 ng/mL
- +3 hours: 5,000 ng/mL
- +6 hours: 2,500 ng/mL
- +9 hours: 1,250 ng/mL
- +12 hours: 625 ng/mL
- +15 hours: ~312 ng/mL
Try the EtG Calculator
Now that you understand the science, use our calculator to estimate your personal EtG levels and clearance time.
Calculate Now