--- title: "How long is cannabis detectable in hair" description: "Learn how long cannabis is detectable in hair tests. AMH Nationwide provides precise THC hair analysis with certified lab review. Call (877) 731-6362." author: "AMH Nationwide" date: "2026-08-28" tags: ["how long is cannabis detectable in hair", "how long is cannabis detectable in hair | how long is thc detectable in hair | how long is weed detectable in hair"] canonical: "https://amhnationwide.com/how-long-is-cannabis-detectable-in-hair/" last_updated: "2026-08-28" --- # How long is cannabis detectable in hair **By AMH Nationwide** | August 28, 2026 Learn how long cannabis is detectable in hair tests. AMH Nationwide provides precise THC hair analysis with certified lab review. Call (877) 731-6362. --- How long is cannabis detectable in hair depends on hair length and growth but generally ranges up to 90 days. Hair testing detects THC exposure over weeks to months, making it useful for long-term substance use analysis. AMH Nationwide uses five national lab networks and certified review. Call (877) 731-6362. [DETECTION WINDOW](https://amhnationwide.com/hair-follicle-drug-test-detection-window/) ## How long is cannabis detectable in hair? Cannabis is typically detectable in hair for up to 90 days after use. Hair testing captures THC metabolites deposited in the hair shaft as hair grows, providing a detection window that reflects approximately three months of exposure. The exact detection period depends on the length of the hair sample collected, usually 1.5 inches representing about 90 days of growth. THC METABOLITES ## What compounds does hair testing detect for cannabis? Hair testing for cannabis detects THC metabolites, primarily 11-nor-9-carboxy-THC (THC-COOH), which is a non-psychoactive byproduct of THC metabolism. These metabolites become incorporated into the hair from the bloodstream during hair formation. Testing does not detect THC itself but its metabolites, which confirms cannabis use. TESTING PROCESS ## How does AMH Nationwide process cannabis hair tests? AMH Nationwide routes hair samples through five national lab networks: [Quest Diagnostics](https://www.questdiagnostics.com/), [LabCorp](https://www.labcorp.com/), Omega Labs, United States Drug Testing Labs, and ExperTox. Each non-negative screen undergoes review by a certified Medical Review Officer (MRO). The labs follow stringent protocols to ensure accurate detection of cannabis metabolites in hair samples. TESTING CONTEXT ## Who orders cannabis hair testing and why? Cannabis hair testing is commonly ordered by employers, courts, [probation](https://amhnationwide.com/hair-follicle-drug-test-probation/) officers, and individuals seeking long-term drug use verification. Hair testing is preferred when a longer detection window is needed compared to [urine](https://amhnationwide.com/urine-drug-testing/) or saliva tests. It is not used for DOT-regulated safety-sensitive roles, which require federally certified urine testing under [49 CFR Part 40](https://www.transportation.gov/odapc/part40). ## Need Cannabis Hair Testing? Contact AMH Nationwide to arrange hair drug testing through our extensive network of collection sites. Call (877) 731-6362 to speak with a representative about your testing needs. [Call (877) 731-6362](tel:+18777316362)[Contact Us](https://amhnationwide.com/contact-us/) LIMITATIONS ## Can hair testing detect one-time cannabis use or passive exposure? Hair testing is more reliable for detecting repeated or chronic cannabis use rather than single use, since metabolite levels from one-time use might fall below detection thresholds. Passive exposure to cannabis smoke is unlikely to produce sufficient metabolite levels in hair for a positive result. Testing laboratories apply scientifically established cutoffs to reduce false positives. TESTING ACCURACY ## Can cannabis hair tests be beaten or evaded? Cannabis hair tests rely on the incorporation of metabolites into hair, which cannot be altered without damaging the hair or invalidating the sample. There are no scientifically validated methods to reliably evade or cheat hair drug tests. AMH Nationwide follows strict collection and lab protocols to maintain test integrity and accuracy. AMH Reviewed & Maintained By AMH Nationwide Customer Service AMH Nationwide is BBB A+ accredited and routes every order through Quest Diagnostics, LabCorp, Omega Labs, United States Drug Testing Labs, or ExperTox, all of which use multiple lab certification agencies and standards such as [SAMHSA](https://www.samhsa.gov/workplace/drug-testing)-aligned laboratory protocols, the ANSI National Accreditation Board for forensic testing and calibration, the College of American Pathologists (CAP), and Clinical Laboratory Improvement Amendments (CLIA). Every non-negative screen is reviewed by a certified Medical Review Officer as part of standard processing before a result is released, and chain-of-custody documentation is maintained on every collection. This page does not constitute medical or legal advice. **Last updated:** July 2026 You May Also Need [Nail Drug TestingNo head or body hair available? A 5-panel fingernail test covers a similar look-back window.Learn more →](https://amhnationwide.com/5-panel-fingernail-drug-test/)[ChildGuard: Environmental ExposureConcerned about a child or loved one? ChildGuard screens for exposure to drugs in their environment.Learn more →](https://amhnationwide.com/5-panel-hair-drug-test-environmental-exposure-childguard/)[Shorten the Detection WindowShortened options like 30 and 60 day hair panels are also available, useful when a urine test’s 1-3 day window is too short.Learn more →](https://amhnationwide.com/30-day-hair-drug-test/)[Hair ETG Alcohol TestAlso need alcohol testing? The hair ETG test screens for alcohol use, and can be added to the same collection.Learn more →](https://amhnationwide.com/etg-and-peth/) Frequently Asked Questions ## Common Questions Hair testing can detect THC use for up to 90 days, whereas urine testing typically detects cannabis use for 3 to 30 days depending on frequency of use. Hair testing provides a longer detection window. Hair color and type may slightly influence metabolite incorporation, but modern testing methods and cutoff levels minimize bias. Labs use scientifically validated procedures to ensure consistent results. Secondhand smoke is unlikely to cause a positive hair test because metabolite levels from passive exposure are typically below detection thresholds used by labs. Hair treatments may reduce metabolite concentrations but generally cannot eliminate them entirely. Labs consider hair condition during analysis to interpret results accurately. A small sample of hair, usually 1.5 inches long from the scalp, is collected following strict chain-of-custody procedures at an authorized collection site. AMH Nationwide directs clients to these sites. Standard cannabis hair tests detect THC metabolites and do not identify synthetic cannabinoids. Separate specialized tests are required to detect synthetic substances. Sources • [SAMHSA – Mandatory Guidelines for Federal Workplace Drug Testing Programs](https://www.samhsa.gov/workplace/drug-testing) • [U.S. DOT – 49 CFR Part 40 – Procedures for Transportation Workplace Drug and Alcohol Testing Programs](https://www.transportation.gov/odapc/part40) • [CDC – National Center for Health Statistics – Drug Use FastStats](https://www.cdc.gov/nchs/fastats/drug-use.htm) • [Quest Diagnostics – Employer Solutions, Hair Testing Methodology](https://www.questdiagnostics.com/) • [LabCorp – Occupational Testing Services](https://www.labcorp.com/) ## Ready to get started? AMH Nationwide provides the lab order and arranges collection nationwide. Every non-negative result reviewed by a certified Medical Review Officer. Call (877) 731-6362 or contact us. [Call (877) 731-6362](tel:+18777316362)[Contact Us](https://amhnationwide.com/contact-us/) --- **Need a drug, alcohol, HIV or STD test?** AMH Nationwide is a national lab testing agency operating since 2004, with more than 20,000 collection sites across the United States. Hair, urine, fingernail and blood testing, panels from 5 through 19, for individuals and employers. - Call: (877) 731-6377 - Find a collection site: https://amhnationwide.com/locations/ - Full page: https://amhnationwide.com/how-long-is-cannabis-detectable-in-hair/