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How long does THC stay in your system?

Sources checked · Fact-checked against the cited sources

Short answer

In published studies, urine tests find THC's main breakdown product for about 3 days after one use and for 30 days or more in heavy daily users.3 Saliva tests look back about 1 to 3 days.2 Blood looks back hours after one use and weeks in some daily users.57 Hair can reflect about 3 months.9

Detection windows by test

Reported detection windows for THC, by test and by how often someone uses. Ranges come from published studies, mostly of smoked cannabis. Sources checked Oct 4, 2026.
TestOnce or now and thenSeveral times a weekDailyHeavy, long-term
UrineAbout 3 days3 5 to 7 days3 10 to 15 days3 30 days or more34
BloodHours (above 5 ng/mL: about 1 to 2 hours)5 Not well studied 7 days or more in some people6 Up to 30 days in some people7
Saliva (oral fluid)Up to about 32 hours28 Not well studied 72 hours or more28 Up to 78 hours6
HairOften not detected9 Not well studied About the last 3 months9 About the last 3 months9

Guides

Estimate: where does your day fall?

Fill in the form to see the published window for one test and one pattern of use. It does not predict your own result.

1 · Test type
2 · How often

Whole days, 0 to 120. Today is day 0.

What a test actually measures

A urine screen looks for THC-COOH, the inactive product the body makes from THC, not THC itself. Federal workplace rules screen at 50 ng/mL and confirm at 15 ng/mL in a second, more specific lab test.1 Those rules abbreviate the metabolite "THCA", which is not the THCA in raw cannabis flower.

A saliva (oral fluid) test looks for THC itself. The federal cutoffs are 4 ng/mL to screen and 2 ng/mL to confirm.2

A hair test reads cannabinoids laid down as hair grows, about 1 cm a month, and finds heavy use far more often than light use.9 Urine screens can also react to delta-8-THC and its metabolites.10

In the studies of people who stopped using, levels fell with time, at very different speeds from person to person.47 This site gives no advice on changing a result.

Sources

Sources checked Oct 4, 2026. Numbers in the text link here.

  1. Substance Abuse and Mental Health Services Administration. Mandatory Guidelines for Federal Workplace Drug Testing Programs. Federal Register 82 FR 7920, January 23, 2017. www.federalregister.gov/d/2017-00979Checked Oct 4, 2026 against the full text: the cutoff table.
  2. Substance Abuse and Mental Health Services Administration. Mandatory Guidelines for Federal Workplace Drug Testing Programs: Oral Fluid. Federal Register 84 FR 57554, October 25, 2019. www.federalregister.gov/d/2019-22684Checked Oct 4, 2026 against the full text: the cutoff table and the THC discussion.
  3. Moeller KE, Kissack JC, Atayee RS, Lee KC. Clinical Interpretation of Urine Drug Tests: What Clinicians Need to Know About Urine Drug Screens. Mayo Clin Proc. 2017;92(5):774-796. doi.org/10.1016/j.mayocp.2016.12.007Checked Oct 4, 2026 against the citation. Editor check of the figures pending.
  4. Lowe RH, Abraham TT, Darwin WD, Herning R, Cadet JL, Huestis MA. Extended urinary Delta9-tetrahydrocannabinol excretion in chronic cannabis users precludes use as a biomarker of new drug exposure. Drug Alcohol Depend. 2009;105(1-2):24-32. doi.org/10.1016/j.drugalcdep.2009.05.027Checked Oct 4, 2026 against the abstract.
  5. Desrosiers NA, Himes SK, Scheidweiler KB, Concheiro-Guisan M, Gorelick DA, Huestis MA. Phase I and II cannabinoid disposition in blood and plasma of occasional and frequent smokers following controlled smoked cannabis. Clin Chem. 2014;60(4):631-643. doi.org/10.1373/clinchem.2013.216507Checked Oct 4, 2026 against the abstract.
  6. Odell MS, Frei MY, Gerostamoulos D, Chu M, Lubman DI. Residual cannabis levels in blood, urine and oral fluid following heavy cannabis use. Forensic Sci Int. 2015;249:173-180. doi.org/10.1016/j.forsciint.2015.01.026Checked Oct 4, 2026 against the abstract.
  7. Bergamaschi MM, Karschner EL, Goodwin RS, Scheidweiler KB, Hirvonen J, Queiroz RH, Huestis MA. Impact of prolonged cannabinoid excretion in chronic daily cannabis smokers' blood on per se drugged driving laws. Clin Chem. 2013;59(3):519-526. doi.org/10.1373/clinchem.2012.195503Checked Oct 4, 2026 against the abstract.
  8. Swortwood MJ, Newmeyer MN, Andersson M, Abulseoud OA, Scheidweiler KB, Huestis MA. Cannabinoid disposition in oral fluid after controlled smoked, vaporized, and oral cannabis administration. Drug Test Anal. 2017;9(6):905-915. doi.org/10.1002/dta.2092Checked Oct 4, 2026 against the abstract, and its findings as summarised in source 2.
  9. Taylor M, Lees R, Henderson G, Lingford-Hughes A, Macleod J, Sullivan J, Hickman M. Comparison of cannabinoids in hair with self-reported cannabis consumption in heavy, light and non-cannabis users. Drug Alcohol Rev. 2017;36(2):220-226. doi.org/10.1111/dar.12412Checked Oct 4, 2026 against the abstract.
  10. Wolf CE, Pokhai AA, Poklis JL, Williams GR. The cross-reactivity of cannabinoid analogs (delta-8-THC, delta-10-THC and CBD), their metabolites and chiral carboxy HHC metabolites in urine of six commercially available homogeneous immunoassays. J Anal Toxicol. 2023;47(8):732-736. doi.org/10.1093/jat/bkad059Checked Oct 4, 2026 against the abstract.
  11. United States Code, Title 7, Section 1639o(1): definition of hemp (delta-9 THC concentration of not more than 0.3 percent on a dry weight basis). www.law.cornell.edu/uscode/text/7/1639oChecked Oct 4, 2026 against the statute text.