If you’ve ever had to take a PEth test, you already know the online info is all over the place. Most lab websites just parrot generic numbers.

I got tired of the guesswork and dug into the actual pharmacokinetic studies to put together some rough estimates of how PEth typically rises and falls.

Here is what the model covers:

Estimated Formation: Projected ng/mL elevation broken down by standard drink count and estimated peak BAC. Clearance by Percentile: Half life curves Cutoff Timelines: Rough day-by-day estimates for dropping below the common 20 ng/mL threshold

(Disclaimer: This is modeled from published research and is meant as an additional resource. There is significant variability from person to person, making it hard to predict exactly where any individual will land. Don’t treat this as exact)

Table 1: Estimated PEth 16:0/18:1 rise after a single drinking episode

Approx. peak BAC (g/dL) 200 lb man, drinks over ~2 h 150 lb woman, drinks over ~2 h Rise in ng/mL: central estimate (middle ~80%) Confidence From a near-zero baseline after weeks of abstinence, reaching 20? 0.02 to 0.04 1 to 2 ~1 ~5 (0 to 15) Fair Rare 0.05 to 0.065 3 to 4 ~2 ~13 (5 to 25) Fair Sometimes (~1 in 4) ~0.08 4 to 5 2.5 to 3 ~35 (15 to 65) Moderate Likely 0.10 to 0.12 5 to 6 3 to 3.5 ~50 (20 to 85)* Low Very likely 0.13 to 0.18 7 to 9 4.5 to 5.5 ~70 (35 to 115)* Low Near certain

*Extrapolated; few controlled data at these levels. About 1 in 10 people will fall above each range.

BAC estimates assume an empty stomach and standard 14 g drinks. Drinking with a meal can lower peak BAC substantially, while large pours or strong beers raise it.

Table 2: PEth 16:0/18:1 half-life percentiles

Percentile Half-life (days) Fastest 3.7 10th ~4.3 20th ~5.1 30th ~5.6 40th ~5.85 Median 6.1 Mean 6.3 60th ~6.4 70th ~6.85 80th ~7.25 90th ~8.6 Slowest 10.4

Source: Helander et al. 2019 (47 patients in alcohol detox), https://doi.org/10.1093/alcalc/agz027

** A few individuals have been recorded with much longer half-lives, up to 20 days, but those are edge cases

Table 3: Very VERY rough guide to days until PEth 16:0/18:1 drops below 20 after a single episode

Assumes you started near zero and drank nothing afterward.

200 lb man, drinks over ~2 h 150 lb woman, drinks over ~2 h Approx. peak BAC (g/dL) Fast eliminator Median eliminator Slow eliminator High end (upper rise + slow eliminator) 1 to 2 ~1 0.02 to 0.04 Usually never reaches 20 Usually never reaches 20 Usually never reaches 20 Usually never reaches 20 3 to 4 ~2 0.05 to 0.065 Usually never reaches 20 Usually never reaches 20 Usually never reaches 20 ~3 days 4 to 5 2.5 to 3 ~0.08 ~3.5 days ~5.5 days ~9 days ~19 days 5 to 6 3 to 3.5 0.10 to 0.12 ~5 days ~9 days ~13 days ~23 days 7 to 9 4.5 to 5.5 0.13 to 0.18 ~8 days ~14 days ~21 days ~28 days

Caveats

Spread is HUGE. At the same breath alcohol level, rises in Stöth 2023 ranged from 6 to 71 ng/mL. These tables give typical values, and any individual can land well outside them. Recent drinking pattern matters. People abstinent for 3 to 4 weeks formed noticeably less PEth than regular drinkers at similar BAC. Multiple episodes are too uncertain to model reliably. You can try adding up each episode from the ranges, but it compounds the error in an already uncertain calculation.

Sources

Schröck et al. 2017, Int J Legal Med 131:153. https://doi.org/10.1007/s00414-016-1445-x Stöth et al. 2023, J Anal Toxicol 47:379. https://doi.org/10.1093/jat/bkad009 Javors et al. 2016, Alcohol Clin Exp Res 40:1228. https://doi.org/10.1111/acer.13062 Hill-Kapturczak et al. 2018, Alcohol Clin Exp Res 42:851. https://doi.org/10.1111/acer.13620 Lopez-Cruzan et al. 2018, Alcohol Clin Exp Res 42:2094. https://doi.org/10.1111/acer.13865 Helander et al. 2019, Alcohol Alcohol 54:251. https://doi.org/10.1093/alcalc/agz027 Stöth, Kotzerke et al. 2022, J Anal Toxicol 46:e232. https://doi.org/10.1093/jat/bkac069 Aboutara et al. 2023, Drug Test Anal 15:104. https://doi.org/10.1002/dta.3376 Herzog et al. 2023, Alcohol Alcohol 58:599. https://doi.org/10.1093/alcalc/agad025 Gnann et al. 2012, Alcohol Clin Exp Res 36:1507. https://doi.org/10.1111/j.1530-0277.2012.01768.x