Production of urinary ethanol after sample collection

As the interest in urine drug testing grows, ethanol is frequently included in drug-abuse screening. Collection of urine for drug testing is less invasive than blood collection and is used to screen employees in a large cross-section of occupations. Because alcohol can be produced from carbohydrates via fermentation, our interest was to determine: (1) if ethanol could be produced in glucose-positive urine (2) under what microbiological conditions would this process occur, and (3) would the urine ethanol concentration be significant. Fourteen urine specimens were selected from the Urinalysis Laboratory of a large medical center. All specimens were tested for ethanol concentration on the day of voiding and were found to be negative (< 0.01 mg/100 mL). Urine glucose concentrations ranged from 0 to > or = 2000 mg/dL. Microbiological examinations were performed on all specimens. Storing the samples at room temperature, five of the specimens produced ethanol over the time course of the study (1 to 21 days) in concentrations ranging from 0.036 to 2.327 g/100 mL. Yeast was identified in the five glucose positive urine samples producing ethanol. Six glucose positive urine samples that did not produce ethanol were found to be yeast negative. Findings indicate that significant ethanol concentrations can develop from glucose and yeast positive urine, after the day of voiding.