What are the most detected substances in workplace drug testing?
The drug positivity rate among employees in the United States remained above the 10-year average in 2024, with marijuana remaining the most detected substance in workplace tests, according to a new report.
The 2025 Quest Diagnostics Drug Testing Index revealed that the urine drug positivity rate in the US workforce is at 4.4% in 2024.
This is slightly lower than the 4.6% recorded in 2023, but remains above the four per cent or higher overall drug positivity rate that has persisted over the past 10 years.
Sam Sphar, Vice President and General Manager of Workforce Health Solutions at Quest Diagnostics, said their findings continue to reflect persistent trends.
"When we talk to employers, they tell us the same thing the Quest data tells us – that drug abuse is an ongoing issue among the American workforce," Sphar said in a statement.
"Many also realise that permissive attitudes around drug use can put their non-substance using employees, not to mention the general public, at risk."
According to the report, drug test positivity varies depending on the circumstance, with testing due to employers' suspicion (for-cause testing) showing a 33.1% positivity rate.
Post-accident drug tests also reached 10.2%, while tests carried out after employees have come back from a drug policy violation yielded a 7.9% positivity rate.
Claire Bryant, Senior Programme Manager of Workplace Wellbeing at the National Safety Council, noted that the positivity rates for these circumstances continue to be elevated despite declining slightly.
"For instance, the Quest data showing that about one in three employees tested for cause were positive for drug use demonstrates opportunities for employers to bolster psychologically safe practices and recovery-supportive programmes, enhancing both employee reporting and safety initiatives," Bryant said in a statement.
The most detected drug substances
Meanwhile, marijuana remained the most detected substance in workplace drug tests, despite a slight decline to a 2.9% positivity rate in 2024.
It is also the highest for post-accident drug tests, with a 7.3% positivity rate last year, according to the report.
Amphetamines were the second-highest detected, with a 1.4% positivity rate in urine drug tests, climbing from 1.3% a year ago.
Fentanyls had a sharp increase from 0.48% to 0.55% in 2024, according to the report. It also found that workforce positivity for fentanyl was 707% higher in random tests compared to pre-employment tests.
About 22% of fentanyl-positive workers were also positive for marijuana, while 16% of them also tested positive for amphetamines.
Suhash Harwani, PhD, Senior Director of Science for Workforce Health Solutions at Quest Diagnostics, described the findings as "worrying."
"It is disturbing to see increased use of fentanyl on-the-job and in combination with other drugs, given fentanyl's extreme potency, which can increase risk of impairment, accidents, and potential overdose," Harwani said in a statement.
"It also raises concern that employees are turning to a dangerous drug like fentanyl after they've passed a pre-employment drug screen, putting the overall wellness of the workforce at risk."
Reducing drug use at work
The US Department of Labor (DOL) said employers can take various measures to prevent substance abuse in workplaces.
"Employee assistance programmes, health and well-being programmes, and unions can be allies in preventing substance use by supporting employee education on substance use and providing information on how to access help for a potential substance use disorder," the DOL said on its website.
Employers should also reduce the risk of injury at work in order to cut down the number of employees who may receive opioids for the treatment of injury-related pain.
"Efforts to reduce workplace stressors and to eliminate or reduce alcohol consumption at company social events may also be helpful in reducing substance use in the workforce," it added.
In the US, federal and non-federal workplaces with a federal contract of $100,000 or more or a federal grant in any amount must have a Drug-Free Workplace Program.
"Drug testing can help reduce substance use among employees and can help identify employees who may have a substance use disorder," the department said on its website.
"In a recovery-ready workplace, positive drug tests are first and foremost an opportunity to engage employees and support them in stopping drug use whenever possible."
