How Long Can Weed Show Up in a Drug Test?
Your friend arrives for his shift at the big-box home improvement store. He clocks in and his manager hands him a cup with a Quest Diagnostics logo on it. “Oh, fuck!” he thinks. As he makes a terrifying trek from plumbing to lighting to that weird aisle of doorknobs on his way to the men’s room, he frantically does some mental math. He stayed off the ganj last weekend, but the Friday before that, he had a few tokes at a bonfire. And last month, he got baked into red-eyed stupor binge-watching Rick and Morty. Are those bong hits out of his system yet? He is seriously considering offering a twenty to the stranger in that stall to fill the cup for him. Just how long does it take for cannabis traces to leave the body? Also, is there a more chill place in this strip mall that’s hiring? Like maybe Game Stop?
How does your body process marijuana?
The body cleans out the traces of cannabinoids through metabolism, and metabolic rates vary widely among individuals.
“Each of us has a unique metabolism that processes cannabis at a different rate,” says Joseph Rosado, a medical consultant to International Cannabis Solutions, a Toronto-based consulting firm for governments, workplaces, and healthcare providers with marijuana-related concerns.
“Even among people of the same gender and age, individual lifestyle choices—such as levels of exercise and eating habits—may affect the amount of time required to pass a drug test.” Water-soluble material, like the traces of cannabis, is held in the fat cells. So those with higher levels of fat content store cannabinoids [more] readily than leaner folks, Rosado says.
Still, if your friend hasn’t toked up at all in a month, he’ll probably pass a urinalysis test. While conducting research to assist drug courts and parole offices in 2005, Paul L. Cary, director of the Toxicology and Drug Monitoring Laboratory at the University of Missouri, found that cannabis detection after 30 days since last use happens, but it’s rare. Frequency of use is also a factor. Cary found that most occasional cannabis consumers, or first-time users, retain detectable traces for only three to four days. Chronic users who have been smoking a few times a week have to refrain from their vape pens or glass pipes for 21 days, on average, to reach a point of pass-ability.
A 1999 study from researchers at Harvard University and McLean Hospital attempted to see how long cannabis traces remained in Willie Nelson-level king stoners, people who said they had smoked marijuana 5,000 times or more throughout their life. In what must have been a herculean show of restraint, 17 of these subjects agreed to abstain for 28 days. Five reached non-detectable levels in the first week. Four more produced clean pee by week two. Another two passed drug tests after the third week. Six peed detectable cannabinoids in week four. The study shows that people in the same usage category process their cannabis traces at different rates. But even serious potheads are usually clean after a month off the grass.
Is it legal for my employer to drug test me?
It’s worth noting that this whole practice of peeing in a jar to maintain employment is a highly questionable leftover from the 1980s war on drugs, and hasn’t shown many definitive benefits to anyone but professional piss collectors at urinalysis labs.
A study on some of the world's heaviest smokers may give us a better understanding of how long marijuana can be detected in urine samples.