Getting the Facts Straight: THCa vs. THC

As marijuana use in the US continues to be seen as less socially and legally taboo, both medical and recreational marijuana markets are being adjusted to further protect public health. Laboratory testing is increasingly becoming a requirement for marijuana or marijuana-infused product manufacturers, leading consumers into a retail environment where the potency of various plant compounds, known as cannabinoids, are represented in percentages.

THCa and THC are the two cannabinoids most directly linked to the “high” users receive after smoking or otherwise heating raw or dried marijuana, but what is the difference?

THC Molecule Drawn Pen
Photo by: Ekaterina_Minaeva/Shutterstock

What It Means to Convert THCa to THC

Expressing the differences between the two cannabis plant compounds can be done by examining the two cannabinoids at the molecular level. THCa, shorthand for delta-9 tetrahydrocannabinol acid, is the carboxylic acid form of THC, also known as delta-9 tetrahydrocannabinol. With regard to THCa, a carboxylic acid describes a molecular structure that includes a carbon and oxygen molecule.

Under normal circumstances, this prevents the psychoactive THC from being readily available. THCa, much like both CBDa and CBD, produces no psychoactive “high” or related euphoria. The process of removing the carbon and oxygen molecules, known as decarboxylation, is done simply by adding heat. It is why eating raw marijuana will not get you stoned, but smoking or otherwise heating it will.

It is also important to note that laboratory labels on medical or recreational cannabis usually list both THCa and THC concentrations. If the THCa is testing at 18% and the THC is testing at 1.5%, it may be easily assumed the product, once activated by heat, will be 19.5% THC. This is inaccurate. THCa percentages must be multiplied by the molecular mass of THC before being translated into final THC potential. In an equation, it looks like this:

THC total = (%THCa) x 0.877 + (%THC)

Interestingly, the analysis released by Kate Welch, pharmacist, suggests THCa can produce at least two clinically significant outcomes more effectively than THC can.


The long and short of it is, THCa and THC play different but complementary roles in the efficacy of the cannabis plant. More than anything else, we need to facilitate more federal funding for research into the miracles that marijuana can work, but that only starts when weed is removed as a schedule 1 narcotic and a healthy conversation can be opened up.