THC breaks down into two main metabolites in your body. The first is 11-hydroxy-THC (11-OH-THC), which is psychoactive and actually more potent than THC itself. The second is 11-nor-9-carboxy-THC (THC-COOH), which is inactive and is the compound most drug tests screen for.
The First Step: THC Becomes 11-OH-THC
When THC reaches your liver, enzymes convert it into 11-hydroxy-THC. A single liver enzyme handles about 91% of this conversion, with a second enzyme responsible for the remaining 9%. This first metabolite still crosses into the brain and produces psychoactive effects. In fact, 11-OH-THC is more potent than the original THC molecule.
This is a key reason edibles feel stronger and last longer than smoking. When you inhale cannabis, THC enters the bloodstream through the lungs and reaches the brain before most of it passes through the liver. When you eat cannabis, nearly all of it travels through the digestive system to the liver first, producing significantly higher blood levels of 11-OH-THC. That larger dose of a more potent metabolite explains the intense, prolonged high that edibles are known for.
The Second Step: 11-OH-THC Becomes THC-COOH
The liver then oxidizes 11-OH-THC into THC-COOH (sometimes written as THCCOOH). This metabolite has no psychoactive effects at all. It’s essentially biological waste, but it’s the most important molecule in cannabis drug testing because it lingers in the body far longer than THC or 11-OH-THC.
Before THC-COOH can be excreted, your body attaches a sugar molecule to it through a process called glucuronidation. This makes the compound water-soluble enough to leave through urine. Interestingly, only about 2% to 3% of the THC you actually absorb ends up leaving as THC-COOH and its water-soluble form in urine. The rest exits through feces after being secreted into bile.
Minor Breakdown Products
Beyond these two primary metabolites, THC also produces smaller amounts of less-studied compounds. Two notable ones are 8-beta-hydroxy-THC and 8-beta,11-dihydroxy-THC. These appear in much lower concentrations in the blood. Researchers have investigated whether they could serve as markers of very recent cannabis use, since 8-beta,11-dihydroxy-THC appears to have a shorter detection window than the main metabolites. Neither compound is currently used in standard drug testing.
Why THC Stays in Your System So Long
THC is highly fat-soluble, and your body stores it in fat tissue. It has been detected in human fat biopsies up to 28 days after the last exposure. No metabolism of THC occurs inside fat cells. The THC simply sits there, bound to stored fats, and slowly diffuses back into the bloodstream over time.
This passive release from fat is the reason THC has such a long elimination half-life. For someone who uses cannabis infrequently, the half-life of residual THC is about 1.3 days. For frequent users, it stretches to 5 to 13 days. THC-COOH has its own elimination timeline: a urinary excretion half-life of roughly 30 hours after a week of monitoring, extending to 44 to 60 hours after 12 days.
Conditions that increase fat breakdown can accelerate THC’s release back into the blood. Animal research has shown that food deprivation and stress hormones promote the breakdown of stored fat, which expels THC from fat cells along with free fatty acids. There are also forensic reports of former cannabis users showing unexpectedly high blood THC levels after significant weight loss.
How This Affects Drug Test Detection
Standard urine drug tests look for THC-COOH (after breaking apart its water-soluble form in the lab). Detection windows vary enormously depending on how often you use cannabis. After occasional use, THC-COOH concentrations stay above the common 15 ng/mL testing threshold for up to 4 days. For chronic, heavy users, the metabolite can remain detectable for weeks or even months.
That wide range comes directly from the fat-storage mechanism. Someone who uses cannabis regularly accumulates larger and larger reserves of THC in their fat tissue, and all of it has to work its way back through the liver and out through urine. Each round of release creates more THC-COOH, extending the detection window well beyond what a single-use scenario would produce.