How long does it take for the psychoactive effects of marijuana to wear off?
Because smoked THC is rapidly transferred into the blood stream, THC levels in the blood rise quickly immediately after inhalation. Depending on the dose, THC typically reaches peak concentrations of more than 100 ng/mL five to 10 minutes after inhalation and then rapidly decreases to between one and four ng/mL within three to four hours. However, the blood serum of moderate to heavy marijuana users may contain more than two ng/mL of THC at 24 or even 48 hours after smoking a single joint, a level that studies have shown does not produce impairment.[4] This is a particular concern for medical marijuana patients who are using marijuana in compliance with state laws and their doctors’ advice, but who would likely test positive for marijuana while sober. The graphic below shows the mean plasma levels of THC and its metabolites (11-OH-THC) and THCCOOH) for six subjects smoking a marijuana cigarette containing 34mg of THC, following several days of abstinence (which would reflect an occasio
