In general, the more cannabis you consume, the longer it will take to leave your system. Fortunately, those who smoke the occasional joint or partake in the herb at a rare event don’t have much to worry about.
Most estimates suggest that it takes around three days for the herb to clear your system before a urine test. Unfortunately, heavy cannabis consumers may have a more difficult time.
Older studies using dated technology have found slightly different results. Cronic consumers can test positive for cannabis in a urine test over two months after their last taste of the herb. One 1985 study found that chronic consumers could test positive up to 77 days after leaving cannabis behind.
For all study participants, the average amount of time was 27 days in urine tests. A later study had a similar finding. The research, published in 1989, found that it took 13 heavy cannabis consumers up to 25 days for the herb to clear their system.