The standard THC-COOH cutoff on a federally regulated urine drug test is 50 ng/mL for the initial immunoassay screen and 15 ng/mL for the confirmatory GC-MS or LC-MS/MS test. A specimen that screens at or above 50 ng/mL is treated as presumptive positive, but it is not reported as positive until it also confirms at or above 15 ng/mL. Non-regulated employers, courts, and treatment programs often use stricter limits, including 20 ng/mL, 15 ng/mL, or even 5 ng/mL. THC-COOH (11-nor-9-carboxy-THC) is the non-psychoactive metabolite labs measure because it stays in the body longer than THC itself.
What is THC-COOH and why do labs test for it?
THC-COOH is the main breakdown product your body creates after THC is metabolized in the liver. It has no psychoactive effect, but it clears slowly, which makes it a reliable marker of past cannabis use. Labs measure its concentration in nanograms per milliliter (ng/mL) of urine, blood, or oral fluid.
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What are the common THC-COOH cutoffs by test type?
- Urine immunoassay screen: 50 ng/mL (federal/DOT standard).
- Urine confirmation (GC-MS / LC-MS/MS): 15 ng/mL (federal/DOT standard).
- Non-regulated urine programs: frequently 20 ng/mL, 15 ng/mL, or 5 ng/mL screens.
- Oral fluid (federal): 4 ng/mL screen, 2 ng/mL confirmation.
- Hair: typically 0.1 ng per 10 mg of hair, roughly 0.1 ng/mg.
- Blood: no federal cutoff; individual labs commonly use 1 to 5 ng/mL.
A 50 ng/mL cutoff is intentionally high to reduce false positives from secondhand smoke and trace exposure. Lower cutoffs catch more users, but they also catch people with minimal, incidental exposure.
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How long does THC-COOH stay above the cutoff?
Detection depends on frequency of use, body fat, metabolism, hydration, and dose. General ranges reported in clinical literature are about 1 to 3 days after a single use, 5 to 7 days after occasional use, and 15 to 30 days or longer in daily, heavy users. Urine holds THC-COOH the longest; blood and oral fluid clear within hours to a few days.
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What actually changes your THC-COOH level?
- Frequency and dose: the biggest factor. Chronic high-dose users store more metabolite in fat tissue.
- Body composition: higher fat mass is linked to slower release and longer detection windows.
- Metabolism and age: faster metabolizers clear the metabolite sooner.
- Hydration: heavy water intake lowers concentration but also triggers dilution flags.
Drinking water does not remove THC-COOH; it only changes how concentrated the urine is. Labs check creatinine and specific gravity, and a specimen with creatinine below 20 mg/dL is usually reported as diluted, which may require a retest.
Do lower cutoffs like 20 ng/mL or 15 ng/mL change the result?
Yes. Someone with a light exposure history might fall between 15 and 50 ng/mL, testing negative on a federal screen but positive under a stricter employer policy. If you are tested for a specific employer, court, or program, ask which cutoff and which lab are being used before you draw conclusions from a home test.
Can CBD or hemp products cause a THC-COOH positive?
Full-spectrum CBD and hemp products can contain small amounts of THC, and repeated use may accumulate enough metabolite to cross a low cutoff. CBD isolate with no detectable THC is unlikely to produce a positive. Product labels do not always match lab results, so treat any THC-containing product as detectable.
Quick summary
Remember the two numbers: 50 ng/mL screen, 15 ng/mL confirm, for standard federal urine testing. Anything above the cutoff is a positive unless the confirmation test comes in lower. This guide is educational and is not medical or legal advice.