If you work—or are hoping to work—for an employer that asks employees to submit to drug tests, the casual decision of whether to smoke when someone passes you a joint at a party suddenly becomes more complicated. Weed can stay in your system for months, and for some, the choice to smoke could make or break their employment. Before entering a situation where your job could be on the line, it’s good to arm yourself with information about how drug tests work (and, just in case, how to get around them).
A survey conducted in September found that nine percent of companies worldwide were getting rid of drug tests or job screenings in order to attract more employees, and some employers are dropping weed from their tests as they realize how many of their employees might use it, according to Kendall Cortelyou-Ward, associate professor and program director for the Masters of Science in Healthcare Informatics program at the University of Central Florida. “Many employers are bending to a change in attitudes, and also the reality that this kind of testing greatly reduced their workforce,” Cortelyou-Ward said.
Still, workplace testing for weed isn’t likely to go away any time soon. “Cannabis is not a performance-enhancing drug with respect to most work tasks,” said Jonathan Caulkins, professor of operations research and public policy at Carnegie Mellon University's Heinz College. “It has obvious adverse effects on things like reaction time and short-term memory, and unlike other substances, it can have those effects much longer after last ingestion because it is fat-soluble, and so hangs around in the body longer.”
Some employers conduct drug tests for the sake of workers’ and customers’ safety in jobs where intoxication might compromise someone’s performance, such as military or factory work. This helps businesses avoid liability for workplace accidents or injuries, explained Jordan Tishler, an instructor at Harvard Medical School and president of the medical cannabis practice InhaleMD. “There are also special jobs that require it under the law, like airline pilots and long-haul truck drivers,” Tishler said.
If you’re concerned about being asked to take a drug test after you’ve used cannabis, here’s what you need to know about the different methods of testing, how they work, when employers ask for them, and whether or not there’s any real way to get around them.
When do workplace drug tests happen?
“Testing can be done as part of an application, to maintain a job, or to go to work that day,” said James Giordano, professor of neurology and biochemistry at Georgetown University Medical Center, who researches pharmacology and drug policy. Typically, employers screen for five drugs: marijuana, PCP, opiates, amphetamines, and cocaine.
Another situation where a drug test might be performed is when someone is arrested for an incident where drug use may be relevant, such as reckless driving. Someone might also be asked to submit to a drug test after a workplace accident, said Codi Peterson, pharmacist and scientific advisor to the medical cannabis publication The Cannigma. “This type of drug test is to screen for impairment, giving the employer insight into whether the employee was impaired during the incident,” said Peterson.
How do weed drug tests work?
Drug tests detect weed by picking up metabolites of THC—that is, byproducts that are formed when the drug gets metabolized—which can show up in your urine, blood, saliva, and hair, said Caulkins, who added, “The standard tests for cannabis are actually looking for metabolites, because the THC itself is broken down into metabolites very quickly.”
Consuming plain CBD before a drug test wouldn’t be a problem, said Giordano, but people should be aware that tests might pick up delta-8-THC, a newly popularized form of THC that’s currently legal and considered milder than the type of THC normally consumed, delta-9-THC. “Where it’s going to get tricky is with the 8-THC compounds,” he said. “They’re right on the edges of what's legal and what's not.” Since the legality of delta-8-THC is under debate in some states, someone may be penalized if it’s found in their system. Typically, employers contract labs and send samples out to them for testing.
What are the different types of drug tests for weed?
Marijuana can be detected through blood, saliva, or hair tests, but the most common type of drug test for weed is a urine test, since these tests are quick, non-invasive, and easy to obtain. The window of time after which they’ll detect cannabis use is somewhat unpredictable: Some people can smoke weed and get a negative urine test after just two or three days, according to Giordano.
However, weed can show up on drug tests for longer. “For cannabis, [the time it can stay in your system] is about one month, but with patients who use regularly, I’ve seen positive urine tests for as long as three months,” said Tishler.
“Hair [tests] can be used, but [those tests are] less reliable and more expensive,” said Tishler. “They also can detect the presence of cannabis and other substances the longest—about three months.”
However, according to Giordano, “Hair is less good at detecting recent use.” It takes a day or two for THC metabolites to show up in hair, he explained. Blood tests are the most accurate type and can detect weed as far out as 25 days (though THC also may stay in the blood for as little as 1-2 days), but are typically only used by law enforcement, since they require you to get your blood drawn.
Saliva tests are the best ones for figuring out if someone has used cannabis recently, since they can detect if you’ve used it as recently as 12–24 hours ago, said Giordano. (According to a study in Drug Testing and Analysis, cannabis is typically detectable in saliva after 1–3 days for occasional users, and up to 29 days for regular users.) These are being used more and more often because they’re quick, non-invasive, and difficult to tamper with, but they’re not as accurate as urine or blood tests.
Rarely, secondhand exposure might be reflected in urine or saliva tests. “If I’m in a small room with people smoking and I stay there for half an hour, I might or might not get high in there, but there is the possibility that it could pop up in my saliva or urine,” said Giordano. If THC is found on a urine or saliva test and the person insists it’s from other people they were around within the past few days, a hair test might be used to see if the person has engaged in long-term cannabis use.
One limitation of all these tests is that they can’t tell when exactly you got high or whether you’re under the influence at the moment. “Unfortunately, no test—laboratory or functional (like roadside sobriety tests)—has been proven to accurately determine impairment at that time of testing,” said Tishler. “There is simply no accurate way to know if some is impaired now. The older tests are still being used and largely thrown out of court.”
Can you cheat a weed drug test?
Some products, like “detox teas” and supplements, claim to pull THC out of the user’s body in preparation for drug tests. “Most are designed to either cause a bowel cleaning, clean the hair of fatty molecules (which is not good for your hair!), or most commonly, designed to help you pee and disguise dilute urine as normal urine (vitamins to make pee yellow, etc.),” said Peterson.
Some “detoxifiers” found in smoke shops may help you beat a urine test for weed, but there isn’t solid evidence behind their efficacy. “There are some commercial products designed to help cheat, but since these are illegal, there’s no testing to show that they work,” Tishler said. Plus, he added, “There is no regulation to protect consumers against such products. Most are ‘proprietary,’ and do not list their ingredients. Further, there are no safety or efficacy tests done on them, so the real answer is we have no idea if they work, or are safe.” Many drug tests for weed anticipate that people will try to cheat. “There are many ways to cheat urine drug screens, but most screening programs are wise to these,” said Tishler.
“There are many ways to cheat urine drug screens, but most screening programs are wise to these,” said Tishler. Some people actually obtain kits containing vials of synthetic urine or other people’s urine in order to pass drug tests, said Cortelyou-Ward. However, there are test strips labs can use to check for synthetic urine, and a study in Drug Testing and Analysis found that five of eight synthetic urine brands could be identified just by observation. In other words, they’re far from foolproof.
Some people attempt to get away with drug use by drinking lots of water to dilute their urine beforehand, but this is also unlikely to work, said Giordano. “The tests are really accurate these days,” he explained. “If what they’re concerned about is people who are using cannabis products, then, characteristically, they're testing with high specificity for cannabis products, and the sensitivity of those tests is really good—they're hard to beat.”
Even if someone were able to cheat a drug test, they’d be breaking the law by doing so, according to Giordano. “If, by law, an individual is required to take a drug test as part of an employment and they're looking to dance around that drug test, that is an illegal action known as malfeasance that could command legal retribution,” he said. This could mean suspension or dismissal from your job, or even a fine or jail time.
The only way to ensure that you don’t get caught using cannabis by your employer is to stop using it for long enough for your body to pass the substance. “Sex, genetic differences in metabolism, body fat percentage, frequency of use, and diet can all influence how fast THC is cleared, so predicting pass or fail is very difficult,” said Peterson.
If you want to know how long it takes weed to leave your body, Tishler suggested conducting your own tests at home. “I recommend that people buy urine test kits from Amazon that are essentially the same as the labs use and test themselves each week until they get negative results,” he said. After that, you can rest assured that your employer won’t likely detect weed as long as you lay off of it until after the test.
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