Urine Drug Tests for THC: Cutoffs and Windows
Urine is the most common drug test for cannabis. It does not look for THC itself but for THC-COOH, a metabolite that can linger from a few days to more than a month. Federal cutoff: 50 ng/mL screen, 15 ng/mL confirmation: for THC-COOH in urine.
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Key Takeaways
- Federal cutoff: 50 ng/mL screen, 15 ng/mL confirmation for THC-COOH in urine.
- Two steps. An immunoassay screen, then GC-MS or LC-MS/MS confirmation of any presumptive positive.
- Windows run from about 3 days to 30+ days depending on how often you use.
- Urine turns positive a few hours after use: about 4–6 hours after smoking in a single-dose study.
What a urine test detects
Urine tests target THC-COOH (11-nor-9-carboxy-THC), the main inactive metabolite of THC. According to Mayo Clinic Laboratories, THC itself clears quickly (half-life under 30 minutes) and is not detectable in urine, while the metabolite typically appears in urine within 60 minutes of a dose and can take as long as 4 hours.
Because the metabolite is fat-soluble and released slowly, urine reflects use over the past several days to weeks, not whether you are intoxicated right now. A positive test confirms exposure, not impairment.
Cutoffs and confirmation
Federal workplace programs follow the HHS Mandatory Guidelines. For marijuana in urine, the initial test cutoff is 50 ng/mL and the confirmatory cutoff is 15 ng/mL of THC-COOH. Urine and oral fluid are the only specimens authorized for federal workplace testing.
The initial screen is an immunoassay. Anything that screens positive is retested by a more specific method, gas or liquid chromatography–mass spectrometry, before it is reported. Private employers outside federal rules can choose other cutoffs; the Mayo Clinic Proceedings review notes some labs screen at 20 ng/mL, which extends the detection window.
Detection times by frequency
| Pattern of use | Mayo Clinic Proceedings review | Mayo Clinic Laboratories |
|---|---|---|
| Single use | 3 days | up to 3 days |
| About 4 times a week | 5–7 days | up to 5 days |
| Daily | 10–15 days | up to 10 days |
| Chronic heavy use | more than 30 days | up to 30 days |
Sources: Moeller et al.; Mayo Clinic Laboratories. In a controlled single-dose study, the last positive urine specimen came an average of 42–58 hours after smoking (maximum 72 hours). After heavy chronic use, StatPearls notes cannabinoids can be detectable in urine for up to 3 months.
CBD products and secondhand smoke
Two situations surprise people. First, CBD products that contain some THC can trip a urine test. In a Johns Hopkins study, pure CBD did not produce a confirmed positive, but vaporized CBD-dominant cannabis containing 3.7 mg of THC did in some samples at federal cutoffs. In a 4-week trial of a full-spectrum CBD product with less than 1 mg of THC per day, 7 of 14 participants tested positive. More in CBD and drug tests.
Second, extreme secondhand exposure can register. Non-users who sat for an hour in an unventilated room with six people smoking produced one urine specimen positive at 50 ng/mL and several at 20 ng/mL; with ventilation, no specimens screened positive.
Common questions
What is the cutoff for THC on a urine drug test?
Under the federal workplace guidelines, 50 ng/mL of THC-COOH on the initial screen, confirmed at 15 ng/mL by a second test. Some labs outside federal programs screen at 20 ng/mL.
How soon after using does a urine test turn positive?
The metabolite usually appears in urine within about an hour and can take up to 4 hours. In a single-dose smoking study, the first positive urine specimens came at an average of about 4 to 6 hours.
Can secondhand smoke make me fail a urine test?
Under extreme conditions it can. In a study of non-users seated for an hour in an unventilated room with six cannabis smokers, one urine specimen was positive at 50 ng/mL and several at 20 ng/mL. With room ventilation, none screened positive.
Sources
- government Federal Register, Mandatory Guidelines for Federal Workplace Drug Testing Programs: Authorized Testing Panels (March 13, 2026) ↗ accessed 2026-10-03
- government SAMHSA, Drug-Free Workplace: Frequently Asked Questions ↗ accessed 2026-10-03
- lab Mayo Clinic Laboratories, Drug Book: Marijuana ↗ accessed 2026-10-03
- study Moeller KE et al., Clinical Interpretation of Urine Drug Tests, Mayo Clinic Proceedings 2017;92(5):774-796 ↗ accessed 2026-10-03
- study StatPearls (NCBI Bookshelf), Cannabis (Marijuana) overview ↗ accessed 2026-10-03
- study StatPearls (NCBI Bookshelf), Clinical Drug Testing ↗ accessed 2026-10-03
- study StatPearls (NCBI Bookshelf), Cannabis Use Disorder ↗ accessed 2026-10-03
- study Niedbala RS et al., Detection of Marijuana Use by Oral Fluid and Urine Analysis Following Single-Dose Administration of Smoked and Oral Marijuana, Journal of Analytical Toxicology 2001;25(5):289-303 ↗ accessed 2026-10-03
- study Spindle TR et al., Urinary Pharmacokinetic Profile of Cannabinoids Following Administration of Vaporized and Oral Cannabidiol and Vaporized CBD-Dominant Cannabis, Journal of Analytical Toxicology 2020;44(2):109-125 ↗ accessed 2026-10-03
- study Dahlgren MK et al., Urinary Tetrahydrocannabinol After 4 Weeks of a Full-Spectrum, High-Cannabidiol Treatment in an Open-label Clinical Trial, JAMA Psychiatry ↗ accessed 2026-10-03
- study Herrmann ES et al., Non-Smoker Exposure to Secondhand Cannabis Smoke II: Effect of Room Ventilation, Drug and Alcohol Dependence 2015;151:194-202 ↗ accessed 2026-10-03