How Accurate Are Hair Follicle Tests for Detecting Alcohol Use?
Hair tests for alcohol look for ethyl glucuronide (EtG) and are best at showing repeated, fairly heavy drinking. In one student study, low drinking often produced no detectable EtG, so a negative result does not prove someone never drinks. Results depend on the cutoff used and the lab method.
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We use your email only for this download.What the test measures
Ethyl glucuronide (EtG) is a product the body makes from ethanol. A research article on hair EtG says it is the most effective tool for widening the detection window for chronic excessive drinking. In that study the lab analyzed the proximal 3 cm of each hair sample, the part closest to the scalp.
Common cutoffs
| Hair EtG | How the article cites the consensus |
|---|---|
| 5 pg/mg or less | Does not contradict self-reported abstinence |
| Over 5 pg/mg | Strongly suggests repeated drinking |
| 30 pg/mg or more | Strongly suggests chronic excessive drinking |
The authors say the 5 pg/mg line is a convention for interpretation, not proof of abstinence.
Where accuracy falls short
- Of the university student samples, 77.1% were negative or at or below 5 pg/mg, and the highest value was 22.6 pg/mg.
- Low consumption often gave no detectable EtG, so drinking “could not be totally excluded” if none was found.
- Hair EtG mainly detects relatively high daily intake, so it is less suited to occasional or binge drinking.
- Among students who reported drinking 3 to 5 days a week, only 12.5% were confirmed by the hair result.
This was a small group of students and the authors say the findings are not general. For a legal or medical test, ask the lab or your doctor which cutoff and method they use.
People also ask
How far back does a hair alcohol test look?
The article we read does not give a time window. It analyzed the 3 cm of hair nearest the scalp.
Can a hair test miss light drinking?
Yes. In the student study low consumption often gave no detectable EtG.
What EtG level means heavy drinking?
The consensus cited in the article is 30 pg/mg or more for chronic excessive drinking and over 5 pg/mg for repeated drinking.
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