Many dispensaries are vending their products with a number termed “Total THC”. This is a mis-marketed value which is meant to impart a larger representation rather than an accurate value. This is being done to imply greater potency and usually bumps the percentage numbers of flower into the attractive >20% range. Those who are not aware of the intricacies of THC often buy their medicine based solely on this number, believing this to be the only, or at least primary, indicator of quality. Those who more fully understand cannabis know that it isn’t the amount of THC which is most desired, but rather a particular whole-plant profile that is right for each individual patient or consumer seeking their preferred physiological response. All of the cannabinoids and terpenes present make this determination, cannabis is so much more than just a THC number.
The cannabis plant does not produce THC directly, instead it produces tetrahydrocannabinolic acid, or “THCA”, which upon heating liberates a CO2 molecule in a process known as decarboxylation to ultimately form THC. This natural THCA in its acid form is not psychoactive, but does have medicinal value, including anti-emetic and anti-inflammatory properties and more, and more people are also speaking about its anti-epileptic effects as well.
Most cannabis testing laboratories today utilize methodology that allows to report both THCA and THC values. There is always a small amount of THC on fresh flowers, usually less than 1%, and it is important to be able to see both forms of this compound, especially so in edibles or topical products. So what then is the “Total THC” reported by some labs and dispensaries? This number is a simply the addition of THCA and THC. Specifically, THCA is directly measured through high-pressure liquid chromatography (HPLC) as gas chromatography, GC, does not directly measure THCA, but decarboxylates it inside of the injection port to form THC. The question remains, then, what benefit does reporting this “Total THC” value provide to patients and consumers? In short, nothing but confusion.
Simply, this combination of readings gives a perceived higher THC number, which less informed patients can then take as indicating a high level of psychoactivity, or otherwise judge the medicine of being higher value. However, “Total THC” does not necessarily indicate anything of scientific value beyond a higher number to take to market.
To understand the medicinal value, one needs to know the specific readings. For example, Concentrate A contains 80.84% THCA and 3.95% THC measured with an HPLC. “Total THC” for Concentrate A would equal 84.79%. A dispensary could honestly round that percentage, and label this as 85% Total THC. The problem, then, is that when fully decarboxylated this material would actually only contain 74.85% THC. [(80.84 * 0.877) + 3.95 = 74.85%]. Oral consumption of this concentrate would only yield 3.95% THC.
This information is critical to getting correct when producing and consuming edibles. If the edible is icing, for instance, and not cooked, then the THCA will stay as it is, and the finished product will have low psychoactivity (assuming the total dose is still small). “Total THC” without the further testing of individual molecules, gives little guidance to the producer of these types of products and could lead to economic inefficiencies as well as patient mis-dosing, both of which are undesired.
There is a tremendous amount of knowledge that is only now coming to light about the effects of Cannabis use in different forms. What is known and what is assumed to be true about medical cannabis will be challenged, quantified, and examined scientifically in the coming years. Patients, doctors, and everyone working in the medical cannabis field will be best served by accuracy and honest assessment of the cannabinoid values and ACCL laboratories feel it is imperative to present this information correctly. Therefore, we have all pledged to present individual THCA and THC values as present in the product, and further, when reporting total available THC, use the correct algebraic equation correcting for the change in molecular weight after decarboxylation: (THCA * 0.877) + THC = THCmax
Submitted by Betsy Gribble, Sequoia Analytical Laboratory
Edited by the ACCL