Newswise — July 7, 2025—Nearly half of cannabis flower products are inaccurately labeled when it comes to potency, with most showing they contain more THC than they really do. Meanwhile, labels on cannabis concentrates tend to be accurate, with 96% shown to match what’s inside.

That’s the takeaway from a new analysis of products sold at dispensaries across Colorado—the first state to legalize recreational marijuana. The study, published this month in the journal Scientific Reports, is the first comprehensive label audit of legal market cannabis to date.

“Cannabis use has complex and wide-ranging effects, and we are working hard to better understand them,” said senior author Cinnamon Bidwell, associate professor of psychology and neuroscience at CU Boulder. “While that research plays out, we should, at the very least, be providing accurate information about the amount of THC in these products.”

The study was funded by the Institute of Cannabis Research, the state’s official cannabis research institute, and conducted in collaboration with MedPharm Research, LLC, a licensed cannabis testing facility, manufacturer and retailer. Under federal law, university scientists are not allowed to handle legal market cannabis for research, so collaborating with industry is critical.

For the study, a secret shopper from MedPharm traveled the state to obtain 277 products from 52 dispensaries across 19 counties. The sampling included 178 flower products and 99 smokable concentrates. No edibles were included in this phase of the study.

The shopper shared label photos with Bidwell’s team. Then the samples, marked only with a number, were tested by MedPharm chemists who hadn’t seen the labels. Data analysis showed that flower products contained on average about 21% THC, or tetrahydrocannabinol—the main psychoactive ingredient in cannabis. Concentrates contained 71% THC on average, with some containing as much as 84%. In the 1980s, the typical THC content in marijuana was around 8%. 

“THC content has increased significantly, and we know that greater THC exposure is likely associated with greater risks, including risk of cannabis use disorder and some mental health issues,” notes Bidwell.

Products were considered “accurately labeled” if they contained within 15% of the THC amount shown on the label—the same threshold the state uses. About 44% percent of flower products failed to meet that standard, with 54 of those products inflating their THC content and 23 containing more THC than the label indicated. Only four concentrate products were labeled inaccurately.

“When it comes to concentrates, I would say Colorado gets a good grade for labeling accuracy, but there are some real issues with flower,” said Bidwell.

The study also looked at several other cannabinoids, including cannabidiol (CBD), cannabigerol (CBG), and cannabigerolic acid (CBGA). Notably, CBG and CBGA, which have been associated with anti-inflammatory and anti-anxiety properties,were more abundant than CBD in products across categories. But Colorado law only requires that companies put CBD levels on the label.

“Focusing on THC on the label can actually do a disservice for consumers, because it creates an environment in which people buy based solely on THC content,” said Bidwell. “Our data suggests that multiple other cannabinoids should also be reported.”

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