Delta-9 tetrahydrocannabinol (delta-9 THC)

Delta-9 tetrahydrocannabinol is the principal intoxicating cannabinoid in cannabis and the compound that defines the legal line between hemp and marijuana.

Delta-9 THC produces its characteristic effects by activating the CB1 receptor in the brain, which is also why it can cause impairment. The plant makes it as THCA, which converts to active THC with heat. Under U.S. federal law, Cannabis sativa containing at most 0.3% delta-9 THC by dry weight is hemp, and anything above that is marijuana, which is why the delta-9 line on a certificate of analysis matters.

Delta-9 THC is not interchangeable with CBD; the two have different receptor activity, different legal treatment, and different safety considerations. Two synthetic forms, dronabinol and nabilone, are FDA-approved prescription drugs, but that approval does not extend to hemp or cannabis products in general. Delta-9 THC is recognized as harmful to dogs and cats, so pet owners should keep THC-containing products out of reach and contact a veterinarian about any suspected exposure.