Study: Trace THC Blood Levels Persist In Chronic Cannabis Consumers

Chronic cannabis consumers may test positive for trace, residual levels of THC in blood for several weeks after ceasing their marijuana use, according to clinical trial data published in the journal of the American Association of Clinical Chemistry.

Thirty long-term, daily cannabis consumers participated in the trial. The mean self-reported daily consumption of cannabis among subjects in the study was ten joints per day.

Of the 22 subjects tested 24 hours following admission into the trial, 12 (59 percent) tested positive for THC levels greater than 1ng/ml, but none tested at levels greater than 5ng/ml. All of the subjects’ THC/blood levels tested below 1ng/ml within seven days following admission.

Investigators reported that subjects’ THC/blood levels “did not always decrease in a consistent manner” and that one subject continued to test positive for trace levels of THC for a total of 33 days.

Authors concluded: “To our knowledge, these are the first blood cannabinoid concentrations in chronic daily cannabis smokers during extended (up to 33 days) continuously monitored abstinence. These data are critical for understanding cannabinoid pharmacokinetics in this population, and for interpreting blood cannabinoid tests.”

For more information, please contact Paul Armentano, NORML Deputy Director, at: paul@norml.org. Full text of the study, “Impact of prolonged cannabinoid excretion in chronic daily cannabis smokers’ blood on per se drugged driving laws,” appears in Clinical Chemistry.

Article republished from NORML