THC metabolism is determined by a complex interplay of genetic, physiological, and lifestyle factors. Two people consuming identical amounts of cannabis can have dramatically diffe
THC is primarily metabolised by the liver enzyme CYP2C9. Genetic variants of this enzyme create slow metabolisers and fast metabolisers. CYP2C9*3 carriers metabolise THC significantly more slowly, extending detection windows. CYP2C9*1 homozygotes (standard) clear THC at the average rate. This genetic variation is not testable without clinical genetic screening. Understanding how THC is processed by the liver puts genetic metabolism in context. Other relevant enzymes include CYP3A4 and UGT1A1, both involved in THC glucuronidation.
Metabolic rate naturally declines with age, meaning older individuals typically clear THC-COOH more slowly than younger individuals with identical use patterns. Hormonal differences affect fat distribution: women generally have higher body fat percentages, potentially extending windows relative to men. Hydration affects urinary concentration without changing total metabolite burden — well-hydrated individuals produce dilute urine that may fall below cutoff sooner. See the detailed guide on how body fat interacts with THC storage. Kidney function affects excretion rate: impaired kidney function slows elimination.
Edibles vs smoking produce different metabolite profiles. Edibles undergo first-pass hepatic metabolism, converting a higher proportion of THC to 11-OH-THC (a more potent and longer-lasting metabolite), which then converts to THC-COOH at higher concentrations. Inhalation bypasses this first-pass effect, producing lower peak metabolite concentrations for equivalent doses. High-potency products — concentrates from strains like OG Kush at 20%+ THC — create proportionally larger metabolite burdens than lower-potency flower.
Medications that inhibit CYP2C9 — including fluconazole, amiodarone, and some statins — slow THC metabolism. Inducers of CYP2C9 like rifampicin accelerate clearance. Liver disease (cirrhosis, hepatitis) significantly impairs THC metabolism. High-fat meals increase THC bioavailability and subsequent metabolite burden by up to 2.5x compared to fasted consumption. Understanding these interactions is part of comprehending the full urine detection window picture. Importantly, delta-8 THC undergoes similar metabolic pathways and similar factors apply.