THC vs THCa Cannabinoids: What’s The Difference?

By Ben Walker -May 25, 2021

Even if you’re new to cannabis, there’s a good chance you’ve heard of THC. THC (tetrahydrocannabinol) is the chemical compound found in cannabis that is responsible for making you feel high. It’s typically one of the most abundant cannabinoids in most cannabis strains and products and is responsible for a host of potential health benefits, including pain relief, appetite boosting, and suppression of muscle spasms.

However, you’ve probably noticed that you can’t just eat cannabis leaves or flowers and feel the effects. You need to smoke it first. That’s because THC isn’t present in raw cannabis plant material. Instead, you’ll find THC-a, which is the precursor to THC. THC-a transforms into THC through a process called decarboxylation — a fancy word for heating. Here’s everything you need to know.

What is THCa? 

Major cannabinoids like THC, CBD and CBC, are all present in the mother of all cannabinoids, CBGa (cannabigerolic acid). As the plant matures, the CBGa is transformed through enzyme reactions into THCa, CBDa, and CBCa.

Basically, any cannabinoid with an “a” at the end of it refers to the untransformed version of the cannabinoids we absorb in our endocannabinoid systems. With that in mind, THCa is the precursor to THC, CBDa is the precursor to CBD, and so on.

For these to transform, they must be exposed to heat or some other force (like pressure) to initiate a process called thermal decarboxylation. This process transforms the molecules and forces them to lose their acidic carbonyl group in their structures. This is why transformed cannabinoids drop the “a”.

Untransformed THCa (tetrahydrocannabinolic acid) or CBDa (cannabidiolic acid) turns into THC (tetrahydrocannabinol) or CBD (Cannabidiol) when exposed to heat.

Cannabinoids can produce a variety of intoxicating and therapeutic effects when they’re heated up, which is why they’re so frequently used via smoking, dabbing, vaporizing, baking into edibles, or extracting into concentrates. These processes trigger the enzyme reaction that causes the transformation.

So what is THC? 

THC is the chemically-altered version of THC-a that becomes active when THC-a is exposed to heat. It doesn’t exist in cannabis on its own.

Where to find THC-a 

THC-a is present in raw cannabis products and even some concentrates. Since THC-a can’t be transformed without heat, you can find it in cannabis flowers. To calculate THC-based potency, cultivators typically multiply the THCa content by the final mass divided by the initial mass. From there they factor in the fact that 30-70% of THCa will be lost or destroyed in the smoking process to get the final potency. This provides a good estimate of THC present in a strain that hasn’t been smoked. That’s why you can find %THC listed on most cannabis products even though the THC hasn’t been activated yet.

THCa can also be found in cannabis concentrates, such as THC-a diamonds for example. Diamonds are formed under pressure in a way that doesn’t activate or transform the THCa into THC. THCa diamonds form under low heat and pressure and are then sold as is or reintroduced to a terpene-rich sauce. Unlike other concentrates that extract THC and THC-v from the plant materials, diamonds form with THC-a. THCa diamonds are non-psychoactive until they’re dabbed and the heat transforms the THCa into THC. Diamonds are one of the most potent forms of concentrates made in a solvent-based extraction, checking in at 90-99% THCa.