Cannabis Law Glossary
Delta-9 THC
Definition
The primary psychoactive compound in cannabis; federally a Schedule I controlled substance above 0.3% dry weight in hemp, and the threshold compound separating legal hemp from federally controlled marijuana.
What Is Delta-9 THC?
Delta-9 tetrahydrocannabinol (delta-9 THC or Δ9-THC) is the primary psychoactive compound in the Cannabis sativa L. plant. It is responsible for the intoxicating effects associated with cannabis consumption and is the compound at the center of nearly all federal and state cannabis regulation.
The 0.3% Threshold
The 2018 Farm Bill defined hemp as Cannabis sativa L. containing no more than 0.3% delta-9 THC on a dry weight basis. Any cannabis plant or product exceeding this threshold is classified as marijuana — a Schedule I controlled substance under the CSA — regardless of its appearance, variety, or agricultural origin. This single threshold creates the legal dividing line between the regulated hemp industry and the state-legal cannabis market.
How the Threshold Works in Practice
The 0.3% threshold applies to the finished product, not the plant at harvest. Processors and manufacturers must test their products at multiple stages. Fluctuations in cannabinoid ratios during drying, curing, and processing can push a compliant harvest into non-compliance. "Hot hemp" — hemp that exceeds 0.3% THC — must be destroyed under federal law.
Total THC vs. Delta-9 THC
Some state and USDA programs have moved toward a "total THC" testing standard that includes THCA (which converts to delta-9 THC when heated). This higher effective threshold creates compliance complexity for hemp farmers and processors selling into states with total-THC testing.
Medical and Pharmaceutical Use
FDA-approved pharmaceuticals contain synthetic THC (dronabinol/Marinol and nabilone) for appetite stimulation and nausea. These are Schedule III and Schedule II substances, respectively, demonstrating that even federal law acknowledges therapeutic applications of THC compounds.
Related Terms
See also: [Delta-8 THC](/glossary/delta-8-thc), [2018 Farm Bill](/glossary/2018-farm-bill), [Hot CBD](/glossary/full-spectrum-cbd), [Cannabis Rescheduling](/glossary/cannabis-rescheduling)
Work With Hoban Law Group
THC compliance at the cultivation, processing, and retail level requires expert guidance. [Schedule a consultation](/consultation?source=glossary&term=delta-9-thc).
Authoritative Sources
Work with Hoban Law Group
Schedule a consultation
Have questions about Delta-9 THC or how it applies to your business? Our team prepares a regulatory briefing before you speak. No cost. No commitment.
Engage Hoban Law Group