The ever-increasing range of cannabis products on the market has been accompanied by varying levels of ∆9-tetrahydrocannabinol (THC) and cannabidiol (CBD) and may confer increased risks for THC-related harm. However, researchers in the United Kingdom argue that the application of standard THC units across all cannabis-containing products and administration methods could alleviate these concerns and support safer use patterns. This conclusion was reported in a new edition of Addiction.

The researchers suggest that standard units for cannabis should be similar to those used to measure alcohol content. They state that these units “should be based on the quantity of active pharmacological constituents.” In contrast, previous efforts to develop standard units have focused on measuring the number of joints or grams of cannabis product; however, these methods have since been deemed inadequate. The researchers propose that the dose of THC, reported in milligrams, should be used to develop standard THC units, which can then be applied across all products and methods of administration.

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However, it is still difficult to infer how standardized THC units can be applied across various cannabis products and methods of administration. Differences in the bioavailability of inhaled vs oral THC adds to this challenge, with oral administration resulting in lower bioavailability and slower absorption compared with inhaled cannabis. The authors indicate that it may not be possible to establish 100% equivalency in subjective effects of standard THC units across different administration routes since individuals may have different cannabis-use behaviors.

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Several states have laws regarding the maximum quantity of THC that can be sold in a single serving of edible cannabis. The risk for excessive dosing of THC is high for edible products, which furthers the need for a standard unit measure. Experimental and ecologic data, the authors wrote, suggest that a standard THC unit of 5 milligrams should be fixed for all cannabis products and administration routes, including edibles. For edible products, this fixed dose would fit within current legislation in many regions of North America.

One limitation to implementing standard THC units is doing so in areas where cannabis use is prohibited. In these areas, it would be difficult to control whether standardized units appear on cannabis products since their use is illicit. In terms of future direction, the researchers suggest studying the implementation of CBD units because CBD is known to reduce the harm of THC consumption. They suggest that including both sets of standard units in guidelines for cannabis products could help consumers avoid the risks associated with excessive THC dosage.

The authors stated that the proposed standard THC unit of 5 milligrams can be “a meaningful standard dose among frequent users, while being low enough to minimize the risk of adverse effects of consuming a single unit among naive users.”


Freeman TP, Lorenzetti V. ‘Standard THC units’: a proposal to standardise dose across all cannabis products and methods of administration [published online October 12, 2019]. Addiction. doi:10.1111/add.14842