Features

THC levels are hard to measure: study

Published on July 25, 2025 by Pat Bulmer

Photo: Contributed

How accurate can THC content listings on cannabis labels be when even cannabis plants don’t have the same amounts of the beloved substance from top to bottom?

“Cannabis is an agricultural product. It’s alive, variable and influenced by its environment, just like any crop. Expecting one statistic like a fixed THC percentage to define it is both unrealistic and misleading,” said Orville Bovenschen, president of Village Farms Canadian Cannabis.

Village Farms just published peer-reviewed research in Scientific Reports, highlighting the natural variability of THC potency within cannabis plants.

“The findings from this study suggest this practice of fixed-number labelling does not account for the biological variability inherent to cannabis plants and misrepresents the actual cannabinoid content a consumer experiences,” a company news release said.

The full study, Variability of Total THC in Greenhouse Cultivated Dried Cannabis, is available online.

The study found THC levels can vary in a single plant.

“Between the top and bottom of plants across three batches, Total THC varied by 4.7–6.1% of actual THC content. Between plants of one cultivar, average Total THC varied by 2.8%,” the Village Farms Canadian Cannabis Research, Development and Lab team said in its study.

“In Canada … labelling for dried cannabis must include a single value, in mg/g, for each of THC and Total THC, that is deemed to be representative of the entire batch. However, it is not well understood how representative the value on the label is of either the potency of the entire batch, or of the dried cannabis in each commercial unit,” the study said.

The Ontario Cannabis Store on its website explained the difference between THC and Total THC on cannabis labels: “THC and CBD refer to the quantity of active cannabinoids contained in the product as purchased. Total THC and Total CBD refer to the levels of active cannabinoids when the cannabis is prepared for consumption.” (ie: lit up)

“For products that are meant to be heated before consumption, like dried flower, the first numbers (THC and CBD) will be considerably lower than the ‘total’ numbers because they represent the inactive state of the purchased product.”

Among plants tested for study: “The top and middle strata were consistently higher in potency than the bottom stratum. Total THC for cultivars ‘K4, ‘F2’, and ‘D15’ ranged by 4.7%, 5.9%, and 6.1%, respectively,” the study said.

“The data presented provides valuable insight into the nature of total THC variation within and across cannabis plants of the same cultivar batch. It is important to be aware of this natural variance when classifying and labelling dried cannabis for both recreational and medical use,” the study concluded. “A single value reported on the label is only one of many possible values and is only representative of the mean occasionally.

“It can be concluded that there is no absolute value for total THC that represents a batch and that reported Total THC can vary substantially within and across plants.”