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Blood Test Tracker

Urine Cannabinoids (THC) Screen

A urine test that looks for the main breakdown product of THC, the active ingredient in cannabis. It shows past use, not whether you are impaired now.

AI-verified against cited sources. Awaiting expert reviewAlso called THC, THC-COOHLOINC 18282-4

What it is

This test looks for THC-COOH, a breakdown product your body makes after you use cannabis (marijuana). It is usually a quick immunoassay screen that reports negative or positive against a cutoff, commonly 50 ng/mL. A positive screen is often checked with a more specific test that uses a lower cutoff, which is 15 ng/mL in U.S. federal workplace programs. The test detects past use. It does not show impairment.

Why it matters

Cannabis tests are used in workplace, pain-management and treatment settings, and in some legal ones. A positive result means THC was used at some point in the past days or weeks, but not when, how much, or whether someone is impaired. Results depend on the cutoff, urine dilution and how often someone uses cannabis, and sometimes on unlabeled THC in hemp or CBD products. Cannabis laws differ between states and federal law, and employers may still act on a positive test in some states.

If it’s high

A positive result means THC-COOH was found at or above the test's cutoff. The usual reason is cannabis use in the past days or weeks. Hemp or CBD products with a little THC in them can also do it. Because screens can sometimes react to other substances, a positive screen is usually checked with a confirmation test.

Common causes

  • Using cannabis in any form, including medical use
  • Frequent or long-term use, since THC breakdown products can linger for weeks
  • CBD or hemp products that contain THC that isn't listed on the label
  • A screen that reacted to a different substance (a false positive), which a confirmation test can sort out

What can help

  • If a positive result is unexpected, ask whether a confirmation test has been done or can be done
  • Tell your clinician, or the person reviewing the test, about any cannabis, CBD or hemp products you use
  • For workplace tests, ask about the review process for positive results

What can affect your result

  • How often and how much cannabis was used (frequent users stay positive longer)
  • The test's cutoff and whether it is a screen or a confirmation test
  • How dilute the urine is
  • THC in hemp or CBD products
  • Body fat, since THC is stored in fat and released slowly
  • The cutoff changes the answer. A common screening cutoff for THC-COOH is 50 ng/mL (U.S. federal workplace programs and Mayo's clinical panel), and confirmation testing uses a lower cutoff (15 ng/mL in federal programs). Other tests use other cutoffs.
  • Very dilute urine can bring a result under the cutoff, and concentrated urine can push it over.
  • Screening immunoassays can react with other substances (false positives), so positive screens are usually confirmed with a more specific test.
  • CBD or hemp products may contain THC that isn't on the label, and that THC can cause a positive result.

Any time. A random urine sample is collected as the collection site instructs. Shows past use, not what is happening now. How long it stays positive varies a lot with how often and how much cannabis was used, body fat, urine dilution and the cutoff. In some frequent, long-term users it can stay detectable for a month or more.

When to talk to a clinician

A urine THC screen is not an emergency test and has no urgent threshold. Talk with the clinician who ordered it about any result you didn't expect, or if cannabis use is affecting your health or daily life.

Questions you could ask

  • What is this test's cutoff, and how long might past use stay detectable?
  • Is a confirmation test available, and what cutoff does it use?
  • Could any product I use, such as CBD or hemp items, explain this result?
  • How will this result be used or reviewed?

Questions people ask

How long will THC show up in my urine?

It varies. With occasional use it clears sooner than with frequent, long-term use, and a lower cutoff or concentrated urine makes a positive result last longer. In some heavy, long-term users it can stay positive for a month or more. Your lab or program can tell you what cutoff it uses.

Can CBD products cause a positive THC test?

They can if the product contains THC, which may not be on the label. Studies attribute most positive tests after CBD or hemp oil to THC in the product itself. If a positive result surprises you, tell the person reviewing it which products you use.

Does a positive result mean I'm impaired?

No. A urine test detects past use. It can't show when you used cannabis or whether you are impaired right now.

Show the science and sources

For clinicians and researchers

An immunoassay screen directed at 11-nor-9-carboxy-THC (THC-COOH), the main urinary metabolite. The HHS Mandatory Guidelines for urine (88 FR 70768, 2023) set an initial test cutoff of 50 ng/mL and a confirmatory THC-COOH cutoff of 15 ng/mL by mass spectrometry. Mayo's Controlled Substance Monitoring Profile also screens at 50 ng/mL by immunoassay (LOINC 19415-9, 'Tetrahydrocannabinol [Presence] in Urine by Screen method') and its LC-MS/MS THC-COOH/creatinine test uses a 5.0 ng/mL cutoff. Urine detects past use, not impairment (J Occup Med Toxicol 2025). THC and its metabolites accumulate in fat, and in extreme cases of chronic use urinary cannabinoids can remain detectable for up to about a month during abstinence, depending on the cutoff and urine dilution; in one published example a chronic user needed 54 days to turn negative at the 50 ng/mL immunoassay cutoff. THC-COOH/creatinine ratios and mathematical models are used in monitored abstinence to separate new use from residual excretion, with limits (J Anal Toxicol 2021). A 2026 systematic review found that cannabinoid-positive tests after CBD or hemp oil mostly come from THC in the products (undeclared, mislabeled or contaminated), and that evidence on CBD converting to THC in the body is mixed.

LOINC 18282-4 (primary), 19415-9, 19381-3, 3427-2, 3435-5, 114171-2. Specimen: urine.

Sources

  1. Mandatory Guidelines for Federal Workplace Drug Testing Programs (urine; final notice), U.S. Department of Health and Human Services (Federal Register, 88 FR 70768) (2023)
  2. Controlled Substance Monitoring Profile, Random, Urine (Mayo test CSMPU), Mayo Clinic Laboratories
  3. THC-COOH Confirmation and Creatinine Ratio, Random, Urine (Mayo test THCCR), Mayo Clinic Laboratories
  4. Pre-employment urine drug screening: examining trends in THC-COOH positivity rates post-legalization of recreational cannabis in California - a retrospective review, Journal of Occupational Medicine and Toxicology (2025)
  5. Implementation of Mathematical Models to Predict New Cannabis Use by Urine Drug Testing: It Is Time to Move Forward, Journal of Analytical Toxicology (2021)
  6. Impact of CBD and hemp oil use on drug test results: a systematic review, International Journal of Legal Medicine (2026)
  7. Drug Testing (MedlinePlus Medical Test), MedlinePlus, U.S. National Library of Medicine

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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