--- title: "How long can thc be detected in hair" description: "Learn how long THC can be detected in hair with AMH Nationwide. Hair testing provides a long detection window for cannabis use. Call (877) 731-6362 for info." author: "AMH Nationwide" date: "2026-08-28" tags: ["how long can thc be detected in hair", "how long can thc be detected in hair | how long can weed be detected in hair | how long can cannabis be detected in hair | how long can pot be detected in hair | how long can marijuana be detected in hair"] canonical: "https://amhnationwide.com/how-long-can-thc-be-detected-in-hair/" last_updated: "2026-08-28" --- # How long can thc be detected in hair **By AMH Nationwide** | August 28, 2026 Learn how long THC can be detected in hair with AMH Nationwide. Hair testing provides a long detection window for cannabis use. Call (877) 731-6362 for info. --- How long can THC be detected in hair depends on hair length and usage but typically up to 90 days or longer. Hair drug testing is a reliable method for detecting cannabis use over extended periods. AMH Nationwide processes hair samples through five national lab networks with certified Medical Review Officers reviewing all results. Call (877) 731-6362 for testing details. [DETECTION WINDOW](https://amhnationwide.com/hair-follicle-drug-test-detection-window/) ## How long can THC be detected in hair? THC can be detected in hair for approximately 90 days or more after use. Hair testing captures the metabolites of THC deposited in the hair shaft as it grows, reflecting drug use over months rather than days or weeks. Hair grows about half an inch per month. Standard hair testing analyzes 1.5 inches of hair from the scalp, representing roughly three months of history. Longer hair can provide a longer detection window, but most tests focus on this standard length. Typical detection window: up to 90 days Hair length analyzed: usually 1.5 inches from scalp Detection based on THC metabolites in hair shaft This extended detection period makes hair testing suitable for employers, courts, and [probation](https://amhnationwide.com/hair-follicle-drug-test-probation/) officers seeking a long-term usage profile. ALTERNATIVE TERMS ## How long can weed, cannabis, pot, or marijuana be detected in hair? The terms weed, cannabis, pot, and marijuana all refer to the same substance containing THC. Therefore, the detection window in hair for each is effectively the same. Hair testing detects THC metabolites regardless of the terminology used. Whether the sample is tested for marijuana, weed, or cannabis use, the detection period remains consistent at about 90 days or more. TESTING PROCESS ## How does AMH Nationwide conduct hair THC testing? AMH Nationwide does not offer online ordering but provides a lab order and directs the requester to one of over 20,000 nationwide collection sites. Samples are collected following strict chain-of-custody protocols. Collected hair samples are sent to one of 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 lab follows [SAMHSA](https://www.samhsa.gov/workplace/drug-testing)-aligned and CAP/CLIA-certified procedures. Every non-negative screen is reviewed by a certified Medical Review Officer to ensure accuracy and reliability. ONE-TIME USE AND PASSIVE EXPOSURE ## Can one-time use or passive exposure be detected in hair? One-time cannabis use can be detected in hair depending on the amount consumed and hair characteristics. Hair testing is sensitive to repeated or chronic use but may detect occasional use if sufficient THC metabolites are present. Passive exposure to cannabis smoke is less likely to produce detectable levels of THC metabolites in hair. Laboratories use cut-off thresholds to differentiate environmental exposure from actual drug use. ## Ready to Schedule Your Hair THC Test? Contact AMH Nationwide to receive a lab order and find a nearby collection site. Call (877) 731-6362 to begin the testing process. [Call (877) 731-6362](tel:+18777316362)[Contact Us](https://amhnationwide.com/contact-us/) DOT AND NON-DOT TESTING ## Is hair testing suitable for DOT-regulated safety-sensitive roles? Hair testing is not approved for Department of Transportation (DOT) safety-sensitive roles. DOT regulations require [urine](https://amhnationwide.com/urine-drug-testing/) drug testing following the federally certified urine protocol under [49 CFR Part 40](https://www.transportation.gov/odapc/part40). Hair testing is used primarily for non-DOT roles or other employment situations where a longer detection window is desired. AMH Nationwide offers urine and hair testing options depending on regulatory requirements. PRICING AND QUOTES ## How much does hair THC testing cost? Pricing for hair THC testing varies based on the testing panel selected and the detection window required. Costs can differ depending on the lab and specific services requested. To obtain an accurate quote and discuss testing needs, contact AMH Nationwide directly. There is no online ordering; lab orders are provided by AMH, and the requester is directed to a collection site. Call (877) 731-6362 for pricing information. 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-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 THC can typically be detected in hair for up to 90 days or longer, depending on hair length and usage patterns. Passive exposure is unlikely to produce a positive hair test because labs use thresholds to distinguish exposure from actual use. No, DOT requires urine testing under 49 CFR Part 40. Hair testing is used for non-DOT roles. A small sample of hair, usually 1.5 inches from the scalp, is collected at a certified site following chain-of-custody protocols. Yes, every non-negative hair test is reviewed by a certified Medical Review Officer as part of standard processing. Yes, one-time use can be detected if sufficient THC metabolites are present, but hair testing is more sensitive to repeated use. 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-can-thc-be-detected-in-hair/