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PEth 16:0/18:1 (Phosphatidylethanol)

A blood marker that forms only when alcohol is in your blood, showing alcohol use over roughly the past two to four weeks.

AI-verified against cited sources. Awaiting expert reviewAlso called POPEthLOINC 97607-6

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What it is

Phosphatidylethanol (PEth) is a molecule that forms in the membranes of red blood cells only when alcohol is in your blood. It builds up as you drink and fades slowly, so it works as a record of alcohol use over about the past two to four weeks. The 16:0/18:1 form, also called POPEth, is the most common one and the one used for the main cutoffs.

Why it matters

Clinicians, liver and transplant teams and some monitoring programs use PEth because it doesn't depend only on memory or on self-report. The result can show whether alcohol was likely present over recent weeks and roughly how much. It does not diagnose an alcohol use disorder or any other condition, and it is best read with your own history and your clinician's judgment.

If it’s high

A higher PEth means alcohol was in your blood regularly over the past few weeks. Higher numbers tend to go with more drinking, but the link is not exact, and two people who drink the same amount can have different results. In the 2022 Basel consensus, 20 to 200 ng/mL is described as moderate intake, and above 200 ng/mL as chronic excessive consumption.

Common causes

  • Drinking alcohol at any point in the last 2 to 4 weeks
  • Regular drinking, since PEth rises with how much and how often alcohol is consumed
  • Heavier or daily drinking, which gives higher numbers and a longer detection window
  • Advanced liver disease, which may make results read falsely high

What can help

  • Talk openly with your clinician about your alcohol use and what your result means for you
  • Ask how alcohol could interact with your medications or your liver health
  • If you want to cut back, ask about counseling, support groups and treatment options
  • If PEth is being used to monitor you, ask what result you and your care team are aiming for

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: up to 20 ng/mL. Source: Drug Testing and Analysis, JHEP Reports, Mayo Clinic Laboratories (via the testcatalog.org mirror).

2022 Consensus of Basel interpretation categories

  • Abstinence or low intakebelow 20 ng/mL
  • Moderate intake20 to under 200 ng/mL
  • Chronic excessive consumption200 and above ng/mL

What can affect your result

  • How much and how often you drank in the last 2 to 4 weeks
  • Differences between people in how their bodies produce and clear PEth
  • Advanced liver disease, which may falsely raise results
  • Which PEth form and which cutoff the lab uses
  • How the sample was collected, stored and shipped
  • Advanced liver disease may cause falsely high PEth results, according to ARUP.
  • Mayo Clinic Laboratories asks that skin be cleaned with a non-alcohol product (such as povidone iodine) before the blood draw.
  • The blood must reach the lab in the right tube and be kept cold or frozen. ARUP allows only 3 hours at room temperature, and Mayo prefers frozen.
  • Labs measure different PEth forms (16:0/18:1 and 16:0/18:2) and use different cutoffs, so compare results only with the same lab and form.

Reflects roughly the past 2 to 4 weeks of drinking, with a half-life of about 4 to 10 days. The window is longer after heavy, long-term drinking.

When to talk to a clinician

Talk with a clinician if you are worried about your drinking or your result. If you drink heavily every day, ask a clinician before stopping suddenly, because alcohol withdrawal can be serious. Call 911 or your local emergency number for seizures, confusion, hallucinations or severe shaking after stopping alcohol.

Questions you could ask

  • What cutoff does this lab use, and how does my result compare?
  • What does this number mean for my health and my medications?
  • Would support or treatment options for alcohol use be worth discussing?
  • How often should PEth be rechecked if it is being used to monitor me?

Questions people ask

What do the 20 and 200 ng/mL cutoffs mean?

In the 2022 Basel consensus, below 20 ng/mL fits abstinence or low alcohol intake, 20 to 200 ng/mL fits moderate intake, and above 200 ng/mL fits chronic excessive consumption. These are guides, not diagnoses, and labs word them differently.

Can one drink make my PEth positive?

It depends on how much was in the drink, on the person and on the lab's cutoff. In small studies, a single large drink sometimes stayed under 20 ng/mL and sometimes did not.

How long after the last drink will PEth return to normal?

PEth can stay detectable for about 2 to 4 weeks after the last drink, and longer after heavy, long-term drinking. Its half-life is about 4 to 10 days.

Show the science and sources

Units

  • 1 ng/mL = 1 ng/mL
  • 1 ng/mL = 0.001422 µmol/L

Open the PEth 16:0/18:1 unit converter

For clinicians and researchers

PEth is a group of phospholipids formed from phosphatidylcholine by phospholipase D in the presence of ethanol, and it is incorporated into red blood cell membranes. The main homologues are PEth 16:0/18:1 (POPEth) at about 37 to 46 percent of the total and PEth 16:0/18:2 (PLPEth) at about 26 to 28 percent (ARUP). The half-life is generally 4 to 10 days with a detection window of 2 to 4 weeks, longer in chronic or heavy drinkers. It is measured in EDTA whole blood by LC-MS/MS (Mayo Clinic Laboratories PETH reports both homologues with a 10 ng/mL cutoff each). The 2022 Consensus of Basel designates PEth 16:0/18:1 as the reference analyte and proposes cutoffs of below 20 ng/mL (0.028 µmol/L) for abstinence or low consumption, 20 to 200 ng/mL for moderate use and above 200 ng/mL (0.28 µmol/L) for chronic excessive intake (as summarized in recent reviews). These cutoffs are consensus-based and widely applied rather than derived from outcome trials. Most US commercial labs report positive at 20 ng/mL or higher, and Sweden applies 35 ng/mL (0.05 µmol/L). Dose-response is imprecise: in one small study of 12 people a single drink of 19 to 45 g alcohol (a US standard drink has about 14 g) produced no detectable PEth, while in another study of nine people one drink of 34 to 72 g produced 35 to 120 ng/mL, though five of the nine started at 20 to 30 ng/mL. ARUP notes that patients with advanced liver disease may have falsely elevated PEth (Nguyen et al., 2018).

LOINC 97607-6 (primary), 74661-0. Specimen: whole-blood.

Sources

  1. Consensus for the use of the alcohol biomarker phosphatidylethanol (PEth) for the assessment of abstinence and alcohol consumption in clinical and forensic practice (2022 Consensus of Basel), Drug Testing and Analysis (2022)
  2. Phosphatidylethanol Confirmation, Blood (test PETH), Mayo Clinic Laboratories (via the testcatalog.org mirror)
  3. Phosphatidylethanol (PEth), Whole Blood, Quantitative (test 3002598), ARUP Laboratories
  4. Assessing alcohol consumption in an era of direct alcohol markers, JHEP Reports (2026)
  5. Integrating Phosphatidylethanol to Enhance Alcohol Quantification in Steatotic Liver Disease and Clinical Trials, Liver International (2026)
  6. Phosphatidylethanol (compound summary), PubChem, National Library of Medicine

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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