PEth blood alcohol testing FAQs

A phosphatidylethanol (PEth) test is the gold standard of blood alcohol tests.

When combined with other blood alcohol tests, a thorough bank of evidence can be gathered regarding an individual’s alcohol use.

In this article, we discuss PEth blood alcohol testing, what it is, and what makes PEth testing so conclusive.

What is phosphatidylethanol (PEth) testing?

A phosphatidylethanol (PEth) test is a type of blood alcohol test that looks for the presence of PEth, an abnormal phospholipid and direct biomarker of alcohol, in a blood sample. PEth requires ethanol (the intoxicating agent in alcoholic drinks) for its production, meaning that it is only present in the body when alcohol has been consumed, providing the most conclusive insight into a person’s drinking patterns.

When combined with other blood alcohol tests such as Carbohydrate Deficient Transferrin (CDT) testing, Liver Function Test (LFT) and Mean Corpuscular Volume (MCV) testing, a thorough bank of evidence can be collated regarding an individual’s alcohol use. Although PEth would always be the most conclusive of the tests, a more in-depth insight can be drawn by considering the results of all tests side-by-side.

This is especially important where the safeguarding of children and vulnerable people is paramount, enabling family law professionals and authorities to act on urgent welfare needs.

What makes PEth blood alcohol testing so conclusive?

Unlike other blood alcohol tests such as Carbohydrate Deficient Transferrin (CDT) tests, Liver Function Tests (LFT) and Mean Corpuscular Volume (MCV) tests, all of which are indirect biomarkers of alcohol that can be affected by pre-existing medical conditions, medications, and more – PEth is a direct biomarker of alcohol.

This means that PEth is only present in the body when ethanol (the intoxicating agent in alcoholic drinks) has been consumed.

PEth production begins in the body as soon as ethanol is consumed and accumulates in the blood with frequent alcohol use, giving it a high specificity (48-89 per cent) and sensitivity (88-100 per cent).

In addition, daily alcohol consumption of more than 60g of ethanol (7.5 units) can clearly be distinguished from lower alcohol consumption, meaning that PEth testing can be used to detect chronic and single-drinking episodes.

The wealth of information provided by a PEth test is what makes it the most essential of all blood alcohol tests, enabling us to monitor abstinence, drinking behaviour, or identify relapse.

It is also the only blood alcohol test that can be undertaken during pregnancy or within two months of the birth.

How far do PEth test results go back?

A PEth test can provide an overview of historic alcohol consumption of up to four weeks.

Furthermore, once PEth is formed in the body, it degrades very slowly, making it an extremely reliable indicator of alcohol use.

Experiments have shown that PEth can be detected in a blood sample in as little as one to two hours after a person has consumed alcohol and can remain in the blood for up to 12 days after a single drinking episode.

What will the results of a PEth test show in terms of alcohol consumption?

The results of a PEth blood alcohol test will show the PEth levels that were present in the blood at the time the person’s sample was collected.

PEth accumulates in the blood with more frequent alcohol consumption, making it possible to determine whether a person has consumed alcohol in small/moderate amounts, or whether there has been excessive drinking in the four weeks prior to the blood sample being drawn.

The below table shows the range of PEth levels that can be measured using an AlphaBiolabs PEth blood alcohol test:

PEth level (ng/ml)
< 20 Abstinence or low alcohol consumption in the past month prior to sample collection
20-210 Social/moderate alcohol consumption in the past month prior to sample collection
> 210 Excessive alcohol consumption in the past month prior to sample collection

AlphaBiolabs offers two types of alcohol test reports: a Certificate of Analysis, which is included as standard and includes a summary of the results, or a Statement of Witness, which is an in-depth report with full analytical results, interpretation, and conclusions, for an additional fee.

While both documents are invaluable for legal proceedings, a Statement of Witness provides the most comprehensive interpretation of the findings, including disclosures provided at the time of sample collection (e.g. how much alcohol the donor drinks in a typical week or how long they have been abstinent, if making such a claim).

Where can I get a PEth test?

Using highly accurate scientific analysis in the form of PEth blood testing, along with CDT, LFT and MCV blood alcohol tests, a case can be made to protect those in need – and reunite families where abstinence has been achieved.

We have extensive experience working with solicitors, social workers, local authorities, and Family Court, providing a range of legal testing services including court-approved blood alcohol testing.

Our nationwide network of professional sample collectors are trained to collect a variety of samples under chain of custody, including blood samples for alcohol testing.

We also offer free sample collection for legally-instructed alcohol tests at our Dublin walk-in centre.

It’s easy to request a quote online now for legal blood alcohol testing.

Alternatively, call our Legal sales team on 01 402 9466 or email and a member of the team will be in touch to discuss your case.

Legal alcohol testing

Learn more about alcohol testing for legal matters, direct from our award-winning laboratory.

Marie Law AlphaBiolabs

Marie Law

Head of Toxicology at AlphaBiolabs

A highly-skilled and respected scientist with over 13 years’ experience in the field of forensics, Marie joined AlphaBiolabs in 2022 and oversees the company’s growing toxicology team.

As Head of Toxicology, Marie’s day-to-day responsibilities include maintaining the highest quality testing standards for toxicology and further enhancing AlphaBiolabs’ drug and alcohol testing services for members of the public, the legal sector, and the workplace sector.

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