Phosphatidylethanol (PEth) Test

What is Phosphatidylethanol?

Phosphatidylethanol (PEth) constitutes a group of abnormal phospholipids that are made of glycerol + two fatty acid chains + phosphate. PEth is only formed in human cells when ethanol (the main alcohol in alcoholic drinks) is present. It is produced in association with some of the disruptive effects of ethanol on cell functioning. PEth production is directly proportional to ethanol intake, increasing with increasing ethanol concentration in the blood. It accumulates in the blood with continuous or frequent alcohol consumption.

PEth occurs in several different cells and tissues, including red blood cells, white blood cells, platelets, liver and brain. However, PEth lipids (fats) accumulate in red blood cells only by attaching to their cell membrane. It, therefore, stays in the blood stream. Blood PEth has at least 48 slightly different forms called isoforms, with PEth 16:0/18:1 and PEth 16:0/18:2 being the most prevalent types in human blood.

Can I get a PEth Test online that I can use at home?

Yes. The Online Clinic can offer a PEth test that uses a self-collect blood sample that has been validated for accuracy.

What is a Phosphatidylethanol test?

The PEth test is used to indicate an unhealthy use of alcohol. PEth is a direct biomarker because it is only formed after alcohol is consumed. The level of PEth in blood correlates to the quantity of alcohol consumed in the previous two weeks. The greater the number of alcoholic drinks in a drinking session, the greater the PEth level; and the greater the number of drinking sessions, the longer the period of detection.

Because of the correlation between alcohol intake and PEth levels, PEth 16:0/18:1 can be used to differentiate between abstinence/light alcohol intake and moderate/unhealthy intake. The test is very specific and sensitive (over 99%); PEth tests can detect lower levels of alcohol consumption over a greater time period compared with other biomarkers.

PEth can be detected in blood around 1–2 hours after intake and for up to 4 weeks prior to a blood sample being collected. PEth levels are detectable for around 3–4 weeks following daily uptake of 50 g ethanol (the amount often associated with heavy/unhealthy drinking); for up to 12 days after one drinking episode; and for up to around two weeks after not consuming alcohol.

PEth concentrations do not differ between the sexes or in relation to age, health status, illness, medications, or any previous drinking habits. This means that false positives are very rare. However, individuals may differ in the amount of PEth that accumulates, regardless that the amount of ethanol ingested is the same and consumption is over the same period.

Why is a Phosphatidylethanol test important?

As a direct biomarker of alcohol, needing ethanol for its production, PEth is considered to be one of the best indicators of recent, chronic or unhealthy patterns of alcohol intake. Indirect PEth biomarkers (e.g., tests for carbohydrate deficient transferrin, liver function test, and mean corpuscular volume) that measure ethanol’s toxic effects are not sensitive enough to detect moderate alcohol consumption or binge drinking.

Who should have their Phosphatidylethanol level tested?

The PEth test can be used by any individual wanting to check their PEth level for any reason, such as for health reasons or for monitoring their drinking habits over time.

The PEth testing is often used when evidence of alcohol consumption/abstinence is required. These include:

• Monitoring by healthcare professionals for medical reasons: where greater diagnostic accuracy is required for patients who are possibly under-reporting alcohol use. For monitoring patients with medical conditions such as liver or pancreatic disease; identifying harmful drinking behaviour, binge drinking, and changes in patterns of drinking; tracking alcohol abstinence in individuals who are undergoing rehabilitation. For use in clinical studies. A PEth test is also recommended as a screening tool for women seeking care for alcohol use within the first three months of pregnancy, since any alcohol consumption during this time is considered a health risk to mother and baby.
• Legal matters and court cases: where self-reporting could be unreliable. Confirmation of drinking or abstinence by legal professionals, social workers and the public in child custody cases and vulnerable person welfare decisions.
• Vehicle and other licensing: for medical assessments of chronic conditions or by the Driver and Vehicle Licensing Agency (DVLA) to prove abstinence or chronic/excessive alcohol consumption as confirmation of ability to drive safely before reinstating a driving licence.
• Employer assessment of the workplace: routine screening of employees to assist in the maintenance of health and safety standards.

How to test for Phosphatidylethanol?

The PEth test is carried out using a blood sample. Blood can be collected from a vein in your arm by a healthcare professional, or from your finger by yourself at home.

The PEth test can be done using a few drops of your blood collected at home. A blood sample self-collection pack, including full instructions on how to collect a small blood sample from a finger, is provided by The Online Clinic. Instructions must be thoroughly read and followed. You collect a few drops of blood from a little finger and into a collection tube. The sample is then sent for analysis to our laboratory. The test results are sent to The Online Clinic for interpretation by a doctor. Your results can be discussed with the doctor if you wish to understand their meaning.

What are normal Phosphatidylethanol test results?

PEth 16:0/18:1 is typically measured as a specific alcohol biomarker in the UK. A ‘normal’ blood sample would show zero PEth, as PEth is produced only when alcohol is consumed.

PEth concentrations are interpreted as follows:

• Less than 20 ng/ml: Abstinence or low (light) alcohol consumption: Light consumption for up to one month prior to blood sample collection.
• 20–200 ng/ml: Moderate (significant) alcohol consumption: Moderate consumption up to one month prior to blood sample collection.
• Greater than 200 ng/ml: High (heavy, excessive) alcohol consumption: Excessive consumption up to one month prior to blood sample collection.

The amount and frequency of drinking alcohol affect PEth results, so that six drinks consumed in one drinking session will result in a higher PEth level than six drinks consumed in three drinking sessions.

Incidental exposure such as through regular use of mouthwash is very unlikely to result in a positive PEth test value (over 20 ng/mL).

How to maintain normal Phosphatidylethanol levels

There is no ‘normal’ level of PEth in the body, as PEth does not occur naturally in the body under normal circumstances.

To keep PEth levels minimal, follow the low-risk drinking guidelines. The NHS guidelines for men and women advise drinking no more than 14 units per week on a regular basis, and that consumption should be spread over at least 3 days, there is several alcohol-free days, and to avoid binge drinking. One unit is defined as 10 ml or 8 grams of pure ethanol.

The recommended international cut-off for High Risk (chronic excessive alcohol consumption) drinking is greater than 60 g of ethanol in one day for men (equating to 7.5 units) and greater than 40 g of ethanol in one day for women (equating to 5 units). This is the point at which risk of a sudden problematic event is increased significantly. A lower value is assigned to women because they become more intoxicated with any given amount of alcohol than men.

References

Ashiru S, Banham J, Webster E, et al. Evaluation and comparison of sensitivity of alcohol biomarkers PEth, EtG and EtPa in civil cases in England 2022–2023. Forensic Sci Int. 2024;363:112173. Available from: https://www.sciencedirect.com/science/article/pii/S0379073824002548.

Bracero A, Maxwell S, Nyanin A, et al. Improving screening for alcohol consumption during pregnancy with phosphatidylethanol. Reprod Toxicol 2017;74:104-107. Available from: https://www.sciencedirect.com/science/article/abs/pii/S0890623817302587.

DNA Legal. PEth Testing: An expert guide. 22 Mar 2023. Available from: https://www.dnalegal.com/blog/peth-testing. Accessed 11 Apr 2026.

Drinkaware. UK low risk drinking guidelines. Available from: https://www.drinkaware.co.uk/facts/information-about-alcohol/alcohol-and-the-facts/low-risk-drinking-guidelines#uklowriskdrinkingguidelines. Accessed 11 Apr 2026.

NHS. Alcohol units. Available from: https://www.nhs.uk/live-well/alcohol-advice/calculating-alcohol-units/. Accessed 11 Apr 2026.

Perilli M, Toselli F, Franceschetto L, et al. Phosphatidylethanol (PEth) in Blood as a Marker of Unhealthy Alcohol Use: A Systematic Review with Novel Molecular Insights. Int J Mol Sci 2023;24(15):12175. doi: 10.3390/ijms241512175. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC10418704/.

Reisfield GM, Teitelbaum SA, Jones JT, et al. Blood Phosphatidylethanol Concentrations Following Regular Exposure to an Alcohol-Based Mouthwash. J Anal Toxicol 2021;45(9):950-956. doi: 10.1093/jat/bkaa147. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC8902915/.

Van Uytfanghe K, Stove CP. Increasing Confidence in a Phosphatidylethanol 16:0/18:1 Cutoff at 20 ng/mL to Support Abstinence or Minor Intake of Alcohol. Clin Chem 2023;69(9):1087–1088. Available from: https://academic.oup.com/clinchem/article/69/9/1087/7222173.

World Health Organisation. International guide for monitoring alcohol consumption and related harm. World Health Organisation, Dept. of Mental Health and Substance Abuse, Geneva, 2000 pp 51-54. Available from: https://www.who.int/publications/i/item/international-guide-for-monitoring-alcohol-consumption-and-related-harm. Accessed 11 Apr 2026.