What a PEth level does — and doesn't — tell you.
PEth (phosphatidylethanol) is the blood test family courts rely on to show whether someone has been drinking over roughly the past two to four weeks. Whether you're deciding to order one or making sense of a result you already have, here's what it can prove, what it can't, and how to get a result that holds up in court — anywhere in the country.
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How a PEth result is reported — and read
Your result comes back as a number measured in nanograms per milliliter (ng/mL) — your report may label it PEth 16:0/18:1. The clearest thing any report tells you is whether that number is negative or positive. Past that line, a higher number means less than most people expect.
| PEth level | How labs report it | What that does — and doesn't — tell you |
|---|---|---|
| Below ~20 ng/mL | Negative | Fits with not drinking — or with drinking too little, or too long ago, to reach the cutoff. A negative doesn't on its own prove zero drinking. |
| ~20 ng/mL and above | Positive | Shows that alcohol was in the body during the testing window. It doesn't show how much, how often, or on what day. |
A higher number generally reflects heavier or more sustained drinking — but only in a rough, general way, because people build up and clear PEth at very different rates. That is why a specific value cannot be turned into a specific amount, frequency, or date of drinking — and the limit cuts both ways: a high number does not prove a precise amount, and a low number does not rule out drinking. And if your case is headed to court, the number itself is only half the story — a result ordered through a doctor's office or insurance can look identical on the page yet not be built to hold up as evidence. Before anyone relies on it, it's worth checking whether that result was built for a courtroom.
If you're facing a test and searching for a way around it, there isn't one — but before you panic, read what a positive result would actually establish. It's less than you fear.
PEth ranges: what the number can and can't tell you
| PEth level (ng/mL) | What it indicates | How much the number alone tells you |
|---|---|---|
| Under 20 | Light drinking or no drinking | Fairly clear — but not proof of zero |
| 20 to under 200 | Drinking has occurred | The gray zone — the number alone can't show how much, how often, or when |
| 200 and over | Heavy alcohol use | Clear |
Range boundaries: Ulwelling W, Smith K. “The PEth Blood Test in the Security Environment: What it is; Why it is Important; and Interpretative Guidelines.” Journal of Forensic Sciences 2018;63(6):1634–1640. The descriptions are TrueTest's.
- Under 20 ng/mL is consistent with light drinking or no drinking. It is not proof of zero: occasional light drinking can stay under 20, drinking in the last few hours may not show up yet, and some labs report down to 8 or 10 ng/mL.
- 200 ng/mL and over is consistent with heavy alcohol use. A level this high isn't reached from a drink or two.
The gray zone: 20 to under 200 ng/mL
Published tables often label this range with a drinking pattern. That overstates what the number shows. A result here means drinking has occurred; where it lands depends on things the number doesn't record:
- How recently the drinking stopped. PEth falls by about half every 4.5 days on average — anywhere from about 2 to 11 days, depending on the person.
- One heavy episode or regular drinking. Either can land in the same place.
- The person. Each body forms and clears PEth at its own rate.
Describing the drinking behind a middle-range number is a job for a retained expert with the full history, not a chart.
What PEth actually measures.
PEth forms inside your red blood cells only when alcohol is actually in your blood. No drinking, no PEth. That's what makes it one of the most reliable alcohol tests there is — it doesn't show up unless real alcohol was there.
Direct, not circumstantial
PEth only forms when you actually drink alcohol. It isn't triggered by hand sanitizer, mouthwash, kombucha, or fumes — so the "it wasn't really drinking" explanations that muddy other tests don't work here.
A pattern, not a snapshot
Because PEth builds up and clears slowly, one result reflects drinking across weeks — not the last few hours. It answers "has this person been drinking in recent weeks," not "were they drinking last night."
How far back a PEth test looks.
PEth can pick up drinking from roughly two to four weeks back. At the ends of the scale, the number says something general — under 20 fits light or no drinking, 200 and over fits heavy alcohol use. Between 20 and 200, the number alone can't show how much or how often. That long reach makes PEth the right tool for one kind of question — but not every question. There's no single "best" alcohol test; there's the one that fits the question you're asking.
| Test | Looks back roughly | The question it answers |
|---|---|---|
| Breath / blood alcohol | Hours | "Is there alcohol in their system right now?" |
| Urine EtG | Up to ~80 hours | "Was there drinking around a specific day or event?" |
| PEth (blood) | ~2–4 weeks | "Has there been drinking over the past few weeks?" |
Not sure whether your court order asks for PEth, EtG, or both? It matters — an order that names the wrong test, or sets a timing window that doesn't fit the test, can undo a perfectly good collection. See our guide to choosing the right family-court test, or call and we'll read the order with you. For a longer, multi-month history, hair testing covers months at a time.
Where PEth fits in a custody or monitoring case.
When the question is whether a parent has truly stayed off alcohol for weeks — not just been sober on test day — a long-reach test like PEth fits. Skipping alcohol the day before doesn't beat PEth the way it can beat a short-window test, and because PEth only forms from alcohol you actually drink, the "it was my mouthwash" answer doesn't apply. When the question is different — did someone drink around one specific day or event — a short-window test like EtG is the one that fits, because its narrow window ties the drinking to that moment. The order should name the test that fits the question being asked.
What matters as much as the test itself is the paper trail. A result only holds up in court if the sample's path — who collected it, when, and how it was sealed and handled — is written down with no gaps. That unbroken record (the "chain of custody") is what turns a lab number into evidence. It's also the line for what we'll speak to: how the sample was collected and what a result does and doesn't prove. Measuring the number is the lab's job; saying what it means for a particular person or case is a retained expert's. If you're an attorney setting up testing for a client — or weighing a result the other side produced — here's how we work.
What a PEth level can't tell you.
Reading a result honestly means knowing its edges. PEth is a strong test, but it is not a timeline and not a measure of amount.
It can't measure or date a drink
PEth reflects your drinking added up over recent weeks. It can't pin down when someone drank, how much, or on what day.
It doesn't measure being drunk
A PEth number says nothing about whether someone was drunk at any given moment. It's a look-back at past weeks, not a roadside sobriety check.
People clear it at different rates
The same number can mean different drinking in different people, because everyone builds up and clears PEth at their own rate. That's the main reason a number can't be read as a set amount — and why reading it is a retained expert's job.
Labs report differently
The lowest value a lab reports, and where it draws the "positive" line, can differ from one lab to another. Your lab's own cutoffs are the ones that count.
Getting a PEth test — here or anywhere in the country.
PEth is a blood test, usually a dried blood spot — a quick finger-stick onto a card — or a regular arm draw. Here's the part most people have backwards: the draw itself is the easy part. Drawing blood is routine. What decides whether a PEth result actually holds up is everything around the draw — the right test named in the order, an unbroken chain of custody (a documented record of how the sample was handled from start to finish), and a clear account of what the result does and doesn't prove. That's the part we're built for — and it's the same work whether you're down the street or across the country.
We collect at our Elk Grove Village office, and we can set up a court-ready PEth collection anywhere in the country through a nationwide collection network. Because the demanding part is the handling and documentation, not the draw, that value travels with it.
That nationwide reach isn't limited to PEth — the same applies to our other court testing, including hair testing (which is always collected in person by a trained collector). If your matter is court-related, our blood draw service is built for exactly this.
PEth questions, answered.
What is a normal PEth level?
Under 20 ng/mL — which US labs usually report as negative — is consistent with light drinking or no drinking, but it isn't proof of zero. At 200 ng/mL and over, a result is consistent with heavy alcohol use. From 20 to under 200, the result shows that drinking has occurred, but the number alone can't show how much, how often, or when. Your own report's cutoffs are what matter, and describing the drinking behind a middle-range number is a job for a retained expert.
Can a PEth level show how much, how often, or when someone drank?
Not precisely. The ends of the scale say something general — under 20 ng/mL fits light or no drinking, and 200 and over fits heavy alcohol use — but no PEth number shows exactly how much a person drank, how often, or when. That limit matters most between 20 and 200. Published tables often put a drinking pattern on that range, but they come from studies where the researchers already knew the drinking; in a real case it's the reverse — you have the number and not the drinking — and the same number can come from very different drinking in different people. Reading a number as a specific amount or date claims more than the test can show.
How far back does a PEth test detect alcohol?
Roughly two to four weeks. At the ends of the scale, the number says something general — under 20 fits light or no drinking, 200 and over fits heavy alcohol use. Between 20 and 200, the number alone can't show how much or how often.
Is PEth a "binge-drinking" test — will one drink make me positive?
No. PEth forms from any alcohol, but a single standard drink — one beer, one 5 oz glass of wine, or one shot — makes only trace amounts that stay below the 20 ng/mL positive cutoff.
Can hand sanitizer, mouthwash, or incidental exposure cause a positive PEth?
No. PEth only forms when you actually drink alcohol and it enters your blood. Alcohol you don't drink — mouthwash, hand sanitizer, fumes — doesn't create it, which is one of PEth's big advantages over some other alcohol tests.
Is PEth better than a urine EtG test?
Neither is "better" — they answer different questions. Urine EtG catches recent drinking over about the last few days and can tie it to a specific event; PEth shows drinking over the last few weeks and only reacts to alcohol you actually drink. Which one fits depends on your question and what your court order says — and some situations call for both.
What does a PEth level over 200 ng/mL mean?
A result of 200 ng/mL and over is consistent with heavy alcohol use during the window — a level this high isn't reached from a drink or two. It still isn't a set amount, a diagnosis, or a sign of being drunk at any given moment, and it can't be worked backward to exactly how much or when someone drank. Describing the drinking behind it for a specific case is a retained expert's job.
Does TrueTest interpret my PEth result?
Not beyond what the laboratory itself reports. The lab analyzes the sample and reports the number and its cutoff, and we'll walk you through what the report says. TrueTest's descriptions of the ranges are on this page, under PEth ranges. Describing the drinking behind a specific result for a case is a retained expert's job — and connecting you with the right one is part of what we do. If you're holding a result you can't fully parse, that's not on you — reports are often written for a different reader. Get in touch and we'll walk through what the lab's report does and doesn't say.
What the order has to say.
An order asking for alcohol testing should name the test, not the substance. “A urine alcohol test” already describes two tests with very different windows, and PEth is a third; an order that names the wrong one, or sets a timing window the test cannot answer, can undo a perfectly good collection. It should also set the interval, because a single PEth result is a look-back at recent weeks and not a schedule.
PEth is a blood test, so the collection provision carries more weight here than it does elsewhere. The order should require forensic collection expressly. A blood draw arranged through a physician or billed to insurance is a diagnostic test — generally no documented chain of custody, no tamper-evident handling — and it will not support the reading this page describes.
The model order names specific tests rather than categories in its panel selections, and its forensic-collection paragraph covers the point above. It carries no PEth-specific paragraph, and its alcohol notice — refrain from mouthwash, hand sanitizer and other alcohol-containing products before testing — is a precaution for tests that incidental exposure can affect. It does not apply to PEth, which only forms from alcohol that has actually been drunk. The detection window and the testing interval are terms to add.