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What you will learn in this post:
THC provides the intoxicating effect its consumers know and love. The cannabinoid is one of many found in the plant, each having complex interactions with the body.
THC-COOH, also known as carboxy THC, is a derivative of THC that plays a significant part in how cannabis affects us. The molecule continues to grow in interest due to its role in drug testing and how long it stays in the body.1
What Is THC-COOH?
So, what is carboxy THC — and what is its role in drug test screening?
The molecule has several names, but its official name is 11-nor-9-carboxy-Δ⁹-tetrahydrocannabinol, which reads as "carboxy THC." It's also referred to as 11-nor-9-carboxy-THC or THC-COOH.
THC itself typically leaves the system within a few hours. What remains are other metabolites or byproducts. THC-COOH is a metabolite of THC, the primary intoxicating cannabinoid. When the body metabolizes THC, it undergoes a series of chemical transformations.
In the liver, delta-9 THC metabolizes into a more potent, intoxicating form: 11-OH-THC, also known as 11-Hydroxy-THC. When it is metabolized further and excreted, it becomes THC-COOH. At this stage, it's inactive and no longer intoxicating.
THC-COOH is primarily excreted in the urine. It's not uncommon for THC-COOH to be detectable for weeks or even months after the last cannabis use.2 This is the reason the cannabinoid metabolite is used as a marker for cannabis use in drug testing, even though it's inactive and non-intoxicating.
Effects of THC-COOH
Because it's an inactive metabolite of THC, THC-COOH provides no noticeable effects.
Unlike THC, it doesn't bind to any receptors in the body. As a result, it doesn't produce any physiological or intoxicating effects. It's not entirely similar to non-intoxicating cannabinoids like CBD either, since they do affect the body in other ways.
THC-COOH is simply a byproduct of THC metabolism. Instead of being water-soluble like most medications, it is lipid-soluble and stored in the fat cells. The metabolite is detectable in the body for weeks or months after the last cannabis use, but its presence doesn't prove current impairment, timing, or the amount of cannabis consumed.
THC-COOH vs. 11-Hydroxy THC
11-Hydroxy-THC and carboxy THC are both important THC metabolites. While they both originate from THC, the similarities stop there. The two molecules have distinct characteristics and roles in the metabolic process.
When inhaled or ingested, THC metabolizes into 11-Hydroxy-THC. It's this molecule that binds to the cannabinoid receptors in the body to produce the characteristic "high" from cannabis use.
Then, the enzymes in the liver metabolize 11-Hydroxy-THC further, eventually forming THC-COOH. The metabolite is inactive and doesn't bind to any receptors. How long it takes to get to this step may help influence how long edibles last.
THC-COOH is the primary metabolite detected in urine and blood screenings for cannabis use. While its presence indicates previous cannabis consumption, it doesn't prove current impairment.
How Does THC-COOH Relate to Drug Testing?
THC-COOH, though non-intoxicating, is the primary metabolite of THC. It remains detectable in the body for an extended period, often weeks after cannabis use. As a result, many drug tests, especially urine tests, specifically look for THC-COOH.
What is a high level of carboxy THC, then?
A positive test result for cannabis is a concentration of THC-COOH greater than 15 nanograms per milliliter (ng/mL) in urine. This cutoff level is according to the US Department of Health and Human Services and other agencies.3 It was established to distinguish between drug use and environmental exposure like secondhand smoke.
Simply put, THC-COOH levels in urine check for previous cannabis exposure. Carboxy THC levels in urine don't imply current intoxication.
Some drug tests may test for delta-9 THC alongside THC-COOH. Others, like oral fluid tests, may not detect carboxy THC but can detect delta-9 THC. The detection of carboxy THC depends on the type of drug test.4
How Long Does THC-COOH Stay in the Body?
It’s unclear exactly how long THC-COOH stays in the body. Carboxy-THC levels in urine can remain detectable for an extended period.
Since THC-COOH is lipid-soluble rather than water-soluble, it's stored in fat cells. While the effects of THC typically only last several hours at max, THC-COOH levels in urine are detectable for weeks or months after use.3
The duration of detection varies widely. Factors that play a role include cannabis use history like the frequency and amount of cannabis consumed.
How long THC stays in the system depends on the type of drug test. For example, THC stays in the hair for longer than it does in urine.
Some consumers utilize various methods to sidestep the risk of positive drug tests. The best way is to abstain or avoid jobs that require drug tests.
References
- Sharma P, Murthy P, Bharath MM. Chemistry, metabolism, and toxicology of cannabis: clinical implications. Iran J Psychiatry. 2012;7(4):149-156. ↩︎
- Lucas CJ, Galettis P, Schneider J. The pharmacokinetics and the pharmacodynamics of cannabinoids. Br J Clin Pharmacol. 2018 Nov;84(11):2477-2482. doi: 10.1111/bcp.13710. Epub 2018 Aug 7. PMID: 30001569; PMCID: PMC6177698. ↩︎
- Connors N, Kosnett MJ, Kulig K, Nelson LS, Stolbach AI. ACMT Position Statement: Interpretation of Urine for Tetrahydrocannabinol Metabolites. J Med Toxicol. 2020;16(2):240-242. doi:10.1007/s13181-019-00753-8 ↩︎
- Hoffman MA, Hubbard JA, Sobolesky PM, et al. Blood and Oral Fluid Cannabinoid Profiles of Frequent and Occasional Cannabis Smokers. Journal of Analytical Toxicology. 2021;45(8):851-862. doi:https://doi.org/10.1093/jat/bkab078 ↩︎
The information in this article and any included images or charts are for educational purposes only. This information is neither a substitute for, nor does it replace, professional legal advice or medical advice, diagnosis, or treatment. If you have any concerns or questions about laws, regulations, or your health, you should always consult with an attorney, physician or other licensed professional.
