A blood–urine comparison from living people cannot establish how xylazine behaves after death. A 2025 Ankara study reported xylazine in urine from 28 people and in blood from seven, but expressly included no autopsy cases. Its useful analytical findings do not validate a postmortem conversion, redistribution factor or lethal concentration.
Which population was actually examined?
Erol Öztürk and colleagues examined blood and urine submitted for forensic testing from suspected drug users during January–December 2024. The paper refers to 9,123 cases or biological submissions and identifies 28 xylazine-positive cases, approximately 0.3%. These were living individuals under law-enforcement supervision, not a series of overdose deaths.
The selected regional population cannot establish national prevalence or a person’s probability of poisoning. One discussion passage prints 0.003%; that conflicts with 28 of 9,123 and the paper’s principal 0.3% result. The smaller printed percentage should not be repeated as a second estimate.
Samples were stored at −20°C. The report does not provide a uniform exposure-to-collection interval or a postmortem anatomical collection site. Those missing details cannot be supplied by assuming that every sample represented the same stage after use.
Detection differed between matrices
The results section reports urine xylazine in all 28 positive cases, ranging from 0.7 to 23.1 ng/mL, and blood xylazine in seven, ranging from 0.5 to 1.1 ng/mL. It reports urinary 4-hydroxyxylazine in 22 and 2,6-dimethylaniline in seven. These are different targets and denominators.
These counts do not supply a validated blood-to-urine equation. The absence of a reported blood detection should also remain distinct from proof that no exposure occurred.
Other substances were frequently detected, but not all findings established simultaneous administration or a mixed product. The investigators lacked route and intent information and stated that investigated seized materials had not demonstrated xylazine adulteration. Biological co-detection alone could not prove a particular drug supply composition.
The limits were analyte- and matrix-specific
The method used solid-phase extraction and LC–high-resolution MS with reference standards and xylazine-d6 internal standard. Table 2 reports the following detection and quantitation limits, respectively: xylazine blood 0.025/0.068 ng/mL and urine 0.05/0.12; 2,6-dimethylaniline blood 0.04/0.11 and urine 0.06/0.19; 4-hydroxyxylazine blood 0.025/0.071 and urine 0.05/0.14.
The calibration series began at 0.05 ng/mL and extended to 100 ng/mL. Inclusion of a low calibrator did not make every analyte quantitatively reliable at that level: the stated quantitation limits were higher. The abstract’s description of analytical-limit ranges is less clear than Table 2, so the explicit table values matter.
Precision and bias were tested at 0.5, 25 and 75 ng/mL with eight replicates; the reported results were within the authors’ 15% criteria. Blood recovery ranged from 72.1–98.4% and urine recovery from 70.3–93.4% across the tested analytes and levels. These laboratory recoveries are not percentages surviving in a body after death.
Short handling tests were not a decomposition experiment
Fortified blood and urine were assessed after 72 hours in an 8°C autosampler, five days at 4°C, and the described five-day freeze/thaw evaluation at −20°C. Peak-area comparisons met the stated ±10% acceptance criterion.
Those conditions do not validate stability through decomposition, a long death-to-autopsy interval or every storage duration. The experiment did not measure postmortem formation, redistribution or tissue release. The authors also could not interpret the observed concentrations against a documented clinical course.
What follows for a death investigation?
The study supports retaining the exact matrix, target and analytical threshold when discussing xylazine findings. It does not show that urine and blood are interchangeable or that their ratio dates use. Detection supplies no automatic impairment or cause-of-death conclusion.
Before applying any published method to autopsy material, establish the laboratory’s validation for the actual specimen and condition. Related distinctions appear in matrix-specific calibration bias and the scope of negative autopsy screens.
Primary source
Erol Öztürk Y, Yeter O, Aslıyüksek H, Oztuna A, Sezigen S, Demirel G. The first report from Ankara on the presence of xylazine abuse in blood and urine samples using a validated LC-HRMS method. International Journal of Legal Medicine. 2025;139:2695–2705. doi:10.1007/s00414-025-03562-7.
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