Estimate Phosphatidylethanol levels based on consumption patterns and detection windows.
Estimated Level: 0 ng/mL
*Disclaimer: This is an estimation tool based on average pharmacokinetic data. Individual metabolism, liver health, and genetics can significantly alter actual lab results.
Understanding PEth (Phosphatidylethanol) Testing
Phosphatidylethanol (PEth) is a direct alcohol biomarker that is formed only in the presence of ethanol. Unlike traditional breath or urine tests that detect alcohol for only a few hours, PEth remains detectable in the blood for significantly longer periods, typically 2 to 4 weeks depending on the intensity of consumption.
How the PEth Calculation Works
The accumulation of PEth in the blood follows a predictable pattern based on the amount of ethanol consumed. Research suggests that for every standard drink (approximately 14 grams of ethanol) consumed daily, a steady-state level is reached over time. The "half-life" of PEth is approximately 4 to 7 days, meaning the level drops by half every week of total abstinence.
PEth Level (ng/mL)
Interpretation
Typical Drinking Pattern
< 20
Negative / Light
Abstinence or very occasional light drinking.
20 – 200
Moderate
Significant social drinking or several drinks daily.
> 200
Heavy / Chronic
Heavy daily consumption or chronic alcohol abuse.
Factors Influencing PEth Levels
Consumption Volume: Higher grams of ethanol per day lead to higher baseline PEth levels.
Duration: It takes roughly 10-14 days of consistent drinking to reach a "steady state" level.
Half-Life: Once drinking stops, the level decays. While the average half-life is 4.5 days, it can range from 3 to 10 days in different individuals.
Body Mass: While PEth is formed in red blood cell membranes, total blood volume (related to body weight) can slightly influence the concentration.
Example Calculation
If an individual consumes 4 standard drinks per day for 14 days, their estimated PEth might peak around 100 ng/mL. If they then abstain for 4 days (one half-life), the level would drop to approximately 50 ng/mL. This calculator uses a kinetic model (22 ng/mL per daily drink factor) adjusted for duration and decay to provide these estimates.
function calculatePEth() {
var dailyDrinks = parseFloat(document.getElementById("dailyDrinks").value);
var duration = parseFloat(document.getElementById("drinkingDuration").value);
var daysSince = parseFloat(document.getElementById("daysSinceLast").value);
var weight = parseFloat(document.getElementById("bodyWeight").value);
if (isNaN(dailyDrinks) || isNaN(duration) || isNaN(daysSince) || dailyDrinks 0) {
weightFactor = 80 / weight;
// Limit the swing of weight factor to avoid unrealistic extremes
if (weightFactor > 1.3) weightFactor = 1.3;
if (weightFactor < 0.7) weightFactor = 0.7;
}
// Half-life of PEth is roughly 4.5 days
var halfLife = 4.5;
// Calculate steady state level for the daily consumption
var steadyState = dailyDrinks * pethConstant * weightFactor;
// Account for duration (Approaching steady state via 1 – e^-kt)
// Rate constant k = ln(2)/halfLife
var k = 0.693 / halfLife;
var peakLevel = steadyState * (1 – Math.pow(Math.E, -k * duration));
// Calculate decay based on days since last drink
var currentLevel = peakLevel * Math.pow(0.5, (daysSince / halfLife));
// Round to 1 decimal place
var finalResult = Math.max(0, currentLevel).toFixed(1);
// Display results
document.getElementById("pethOutput").innerText = finalResult;
var interpretation = "";
var color = "";
if (finalResult = 20 && finalResult <= 200) {
interpretation = "Status: Moderate Consumption. Consistent with regular social drinking or significant recent intake.";
color = "#d69e2e";
} else {
interpretation = "Status: Heavy / Chronic Consumption. Suggestive of heavy daily drinking or chronic excessive use.";
color = "#e53e3e";
}
var interpDiv = document.getElementById("pethInterpretation");
interpDiv.innerText = interpretation;
interpDiv.style.color = color;
document.getElementById("pethResultBox").style.display = "block";
document.getElementById("pethResultBox").style.borderLeftColor = color;
}