Among the many benefits offered to Canadian patients under the Marihuana for Medical Purposes Regulations is the assurance that every lot of medical cannabis sold has undergone strict quality control testing to ensure it is free of contaminants such as bacteria, mould, and heavy metals. In addition, Health Canada provides guidance to Licensed Producers to assure uniformity in the industry with respect to such matters as potency testing.

As of this month, Tilray is changing the way it reports levels of THC and CBD in dried cannabis. Previously, our method was to report total THC, which was obtained by adding 2 numbers together: the THC present in dried plant matter, as well as the THCA present in that same plant matter. For example, if we produced a batch of White Widow with 1.1% THC and 24.3% THCA, we would have applied the following equation to obtain a total THC value of 25.4 %:

THC (1.1%) + THCA (24.3%) = Total THC (25.4%)


This method of calculating the total THC was used not only by our in-house laboratory at Tilray but also by third-party laboratories that verified our potency results.

However, recent clarification from Health Canada has led us to change the way we report potency on the labels of our dried flower and House Blend products. Instead of total THC calculated from the actual THC and THCA present in the plant matter, we are reporting the amount of “active” THC. The amount of active THC is a lower number than the amount of total THC. This is because the THCA present in dried cannabis loses approximately 12.3% of its mass (in the form of carbon dioxide) when it is decarboxylated to become THC (i.e. during combustion or extraction).

The active THC number is calculated using a different equation, so the label for the same White Widow sample referenced above would show a different value of 22.4% THC. Here is the equation used to calculate active THC:

THC (1.1%) + THCA (24.3% x 0.877) = Active THC (22.4%)


The same change applies to our reporting of CBD levels, as CBD’s precursor, CBDA, also loses mass when it is decarboxylated. The same equation is now being used to calculate the “active” CBD in cannabis. For instance, if we produced a batch of Elwyn with 1.2% CBD and 10.2% CBDA, we would now apply the following calculation to obtain an active CBD level of 10.1%:

CBD (1.2%) + CBDA (10.2% X 0.877) = Active CBD (10.1%)


What does this mean for medical cannabis patients? Starting soon, potency numbers will appear to decline slightly across all dried cannabis strains, as product labels will bear active cannabinoid (THC and CBD) levels rather than total cannabinoid levels. However, in order to help our patients understand how active cannabinoid levels relate to total cannabinoid levels, we will display the raw values of THC and THCA, as well as CBD and CBDA, on our product pages.