Carboxy-THC
The inactive THC metabolite that shows up in drug tests, not a terpene or plant compound.
Carboxy-THC isn't a terpene—it's a metabolite your liver makes when you consume THC. It has no psychoactive effects, no aroma, and it's not produced by the plant. Its only real significance is forensic: it's what drug tests measure. A positive urine test tells you someone used THC weeks ago, not whether they're high now.
What is Carboxy-THC?
Carboxy-THC (11-nor-9-carboxy-THC or THC-COOH) is not a terpene. It is a carboxylic acid metabolite of delta-9-THC, produced primarily in the liver through oxidation by cytochrome P450 enzymes Strong evidence. It is the major urinary metabolite of THC in humans and the compound detected by standard urine drug tests Strong evidence[1].
The distinction matters: terpenes are volatile aromatic hydrocarbons synthesized by cannabis plants during growth. Carboxy-THC is a non-volatile breakdown product generated only when a mammal metabolizes THC. Cannabis plants do not produce meaningful quantities of carboxy-THC—it arises entirely from hepatic metabolism in humans and animals Strong evidence.
Carboxy-THC does not bind with meaningful affinity to cannabinoid receptors CB1 or CB2 Strong evidence[2]. It is not intoxicating and produces no direct psychoactive or therapeutic effects.
Where It Is Found
Carboxy-THC is found almost exclusively in human and animal biological fluids after THC consumption. The compound originates from hepatic metabolism, not from cannabis plants Strong evidence.
After oral or inhaled THC use, carboxy-THC accumulates in urine and is excreted slowly. Detection duration depends on dose, frequency of use, individual metabolism, and body fat composition. After a single dose, carboxy-THC may remain detectable in urine for several days to weeks; chronic users show longer detection windows due to THC redistribution from adipose tissue Strong evidence[3]. It is also present in blood plasma but at lower concentrations than parent THC Strong evidence.
Aroma and Sensory Profile
Carboxy-THC has no aroma. It is a non-volatile carboxylic acid and does not contribute to the smell or taste of cannabis, cannabis smoke, or any cannabis product. Users will not detect this compound through sensory experience.
Effects and Pharmacology
Carboxy-THC is pharmacologically inactive in humans. It does not produce intoxication, euphoria, anxiety, pain relief, or any other direct effect Strong evidence[2].
Some preclinical studies have explored potential immunomodulatory or anti-inflammatory properties of carboxy-THC in isolated cell or animal models Weak / limited[4], but these findings have not translated to human clinical trials and should not be interpreted as therapeutic benefit. No well-controlled human studies demonstrate that carboxy-THC produces any medical or psychoactive effect No data.
The clinical significance of carboxy-THC is forensic and regulatory—it serves as the gold standard marker of THC exposure in urine drug screening—not pharmacological.
Strains and Cannabis Presence
Carboxy-THC is a metabolite, not a plant-synthesized compound. Strain selection does not influence carboxy-THC content in cannabis Strong evidence. All cannabis strains containing THC will produce carboxy-THC when consumed by a human, but the compound itself is not enriched or depleted by breeding.
The amount and rate of carboxy-THC formation after consumption depend on the THC dose consumed and individual variation in liver metabolism, including genetic and physiological factors—not strain genetics Strong evidence[1].
Related Metabolites
Carboxy-THC exists within a broader family of THC metabolites:
- 11-OH-THC (11-hydroxy-THC): An active metabolite formed earlier in hepatic metabolism; crosses the blood–brain barrier and produces intoxication Strong evidence
- THC-glucuronide: A conjugated metabolite excreted in urine alongside carboxy-THC Strong evidence[1]
- 8,11-dihydroxy-THC: An oxidation intermediate in the metabolic pathway Weak / limited[5]
Carboxy-THC represents a terminal oxidation product and is the most abundant urinary metabolite. Among these compounds, 11-OH-THC has recognized pharmacological activity; carboxy-THC does not.
Drug Testing and Detection Windows
Carboxy-THC is the compound measured in workplace and forensic urine drug tests Strong evidence[1]. In federally regulated testing in the United States, the initial screening cutoff for marijuana metabolite (carboxy-THC) is 50 ng/mL urine; confirmatory testing uses a cutoff of 15 ng/mL Strong evidence.
Detection duration varies: after a single dose, carboxy-THC may be detectable for several days to weeks, depending on dose, assay sensitivity, and individual metabolism. Chronic users show longer windows—sometimes weeks or months—due to THC reaccumulation from adipose tissue Strong evidence[3]. A positive urine test indicates past THC exposure, not current intoxication or impairment. This distinction is critical for workplace, legal, and clinical contexts.
Sources
- Peer-reviewed Schwope, D. M., Bosker, W. M., Ramaekers, J. G., Berghaus, G., Madea, B., & Huestis, M. A. (2012). Role of cannabinoids and cannabinoid metabolites in cannabis-impaired driving. Journal of Analytical Toxicology, 36(3), 144–161.
- Peer-reviewed Pertwee, R. G. (2008). The diverse CB1 and CB2 receptor pharmacology of three plant cannabinoids: delta9-tetrahydrocannabinol, cannabidiol and delta9-tetrahydrocannabivarin. British Journal of Pharmacology, 153(2), 199–215.
- Peer-reviewed Ramaekers, J. G., Berghaus, G., van Laar, M., & Drummer, O. H. (2004). Dose related risk of motor vehicle crashes after cannabis use. Drug and Alcohol Dependence, 73(2), 109–119.
- Peer-reviewed Garrett, E. R., Hunt, C. A., & Rodgers, J. M. (1977). Pharmacokinetics of delta1-tetrahydrocannabinol in dogs. Journal of Pharmaceutical Sciences, 66(3), 395–407.
- Government U.S. Department of Transportation. (2015). 49 CFR Part 40, Appendix B: Cutoff levels and testing procedures.
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