We previously explored how cannabinoid content is displayed on cannabis labels in some Canadian provinces, such as BC. Whether those quantities are given as a percentage or in milligrams per gram, two different values of THC and CBD can be strangely advertised. We will explain the differences between THC and the THC total based on Health Canada’s compliances and beyond.

Dr. Roggen demands precision in his cannabis-approved research lab.

D9 versus Total THC

As detailed in our previous installment, we spoke with CLN’s contributing scientist, Dr. Markus Roggen, to gain a more precise understanding of cannabis labelling. We were surprised to learn the involvement behind interpreting a THC quantity from a licensed lab to a consumer.

Legal cannabis labels are filled with perplexing gimmicks and characteristics across Canada. Why is THC separated from Total THC?

The reason behind that is cannabis flower producers THC acid [THCa]. So, if you buy flower it will have say 21% THC acid and maybe 2% [D9] THC. If you were to only label THC, you would have flower with 2% THC, no one would buy that. But, if you displayed THC acid, no one would care.

Dr. Roggen

Can you just add THC and THC acid together for a Total?

Right, so there’s a problem with that. We read the weight in percentage. So, it’s the weight of those molecules divided by the weight of the flower. But, THC acid is a bigger molecule than THC. In decarboxylation, you account for the weight loss as THC acid turns into THC. The weight decreases by 12.3%. So, if you have 21% THCa and 2% THC and you actually decarboxylate that flower, it will not be 23% THC. It will only be 22% THC because of the loss of weight as you decarboxylate THC.

So, that’s why you need to do Total THC as a correction for the weight loss of THC acid turning into THC.

Dr. Roggen
THC and Total THC

Inflating THC’s weight

THCa turns into the intoxicating D9 form while it is smoked or cooked (decarboxylated). Typically, the 12.3% drop in weight has been accounted for when we see a THC percentage on the black market.

When we emailed BCLDB and asked if their Total THC values will seem inflated compared to the black market. They responded to say we will have to follow-up with a licensed producer. Yet, they detailed that,

Minus 12.3% is now thought to be variable and we cannot offer an explanation on this ourselves.


Thankfully, a founder and CEO of an approved cannabis research lab with a Ph.D. in Chemistry, such as Dr. Roggen, is more familiar with the process.

So way back, the black market added the two percentages of THC and THCa [post-calculation]. That’s the same thing as Total THC on Canada’s cannabis labels.

Dr. Roggen

Total THC = (THCa x 0.88) + D9 THC

So, the legal market has adopted the black market’s strategy but has simply left an additional piece of data. THC simply denotes the trace amount of active THC before it is smoked or activated, whereas the Total THC consists of the total amount of active THC post-decarboxylation.

Who asked an expert to start counting the molecules in my weed?

Overall, how accurate is this decarboxylation equation when used to display THC quantities?

It has a duty for end consumers but it’s not a good way to regulate cannabis flower.

Because, what we did is, we had twenty molecules of THC acid and two molecules of THC. They both have weight. So, THC has a weight of one and every molecule of THC acid has a weight of, let’s say 1.1 since THC acid is a little bit heavier.

If we think about it that way, you can just say from the beginning there were 20 molecules of THC acid and two molecules of THC. I don’t care about how much they weigh. In total there were 22 THC molecules.

Dr. Roggen

This seems straightforward. So, why is the method not employed?

The end consumer is not familiar with ‘number of molecules’ (moles) as a measurement. So, using [moles] might be complicated and thats why the industry uses % weight. I think there is a better way to describe THC concentrations in cannabis products, but I am still working on the fine points. I hope to publish on this topic soon.

Dr. Roggen

Thank you for your time, Dr. Markus. End of phone call.

Raw cannabis, doses with hidden intoxicants

Consumers that want raw cannabis without the stone will also benefit when THC acid and D9 THC are displayed as separate values, either in mass or molecules. People are sometimes advised to consume raw cannabis products as a source for THCa. The raw cannabinoid has grand therapeutic benefits not associated with CBD but with the same lack of intoxication. Yet, raw cannabis products, especially rosin, contain a small amount of active THC, not just THCa.

Most generic black market labels do not decipher between active and inactive THC. However, large doses of raw cannabis can cause accidental intoxication which will be avoided by displaying the amount of (D9) THC as a second figure. In the worst-case scenario, tune into the second season of Dr. Roggen’s show, Ask an Expert, broadcast on CLN to find out what happens when you do overconsume active THC.

Stay tuned and will explain how THC and Total THC can help identify extracts and pinpoint potential fake shatter.

Let us know if cannabis labels with THC and Total displayed separately have either helped or confused you. How do you feel cannabinoid values should be displayed?