--- title: "How long does weed stay in a hair follicle test" description: "How long does weed stay in a hair follicle test? Hair testing detects THC use up to 90 days. Call (877) 731-6362 for lab testing info and scheduling." author: "AMH Nationwide" date: "2026-08-28" tags: ["how long does weed stay in a hair follicle test", "how long does weed stay in a hair follicle test | how long does weed stay in hair follicle test | how long does weed stay in hair for drug test | how long does weed stay in hair test | how long does weed stay in hair drug test | how long does weed stay in a hair test | how long does weed stay in your hair test | how long does weed stay in your hair follicle test | how long does a hair test detect weed | how long does weed stay in hair follicle drug test"] canonical: "https://amhnationwide.com/how-long-does-weed-stay-in-a-hair-follicle-test/" last_updated: "2026-08-28" --- # How long does weed stay in a hair follicle test **By AMH Nationwide** | August 28, 2026 How long does weed stay in a hair follicle test? Hair testing detects THC use up to 90 days. Call (877) 731-6362 for lab testing info and scheduling. --- How long does weed stay in a hair follicle test? THC metabolites can be detected in hair follicles for up to 90 days after use. Hair drug testing is a reliable method for identifying past marijuana consumption over an extended period. AMH Nationwide directs clients to national lab networks for testing. Call (877) 731-6362. [DETECTION WINDOW](https://amhnationwide.com/hair-follicle-drug-test-detection-window/) ## How long does weed stay in a hair follicle test? Weed, or THC, can be detected in hair follicle tests for approximately 90 days after use. Hair testing analyzes the presence of THC metabolites embedded in the hair shaft, which grows about half an inch per month. This allows labs to detect drug use over a three-month period. The 90-day detection window is standard because hair samples typically measure 1.5 inches from the scalp, representing about three months of growth. Testing beyond this period is less reliable due to hair length and environmental exposure. TESTING PROCESS ## What is the procedure for a hair follicle drug test for weed? A hair follicle drug test involves collecting a small sample of hair, usually from the crown of the head. The sample is 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, or ExperTox for analysis. The lab tests the hair for THC metabolites. Every non-negative result is reviewed by a certified Medical Review Officer (MRO) to confirm accuracy and rule out alternative explanations. Clients cannot order tests online; AMH Nationwide provides the lab order and directs to collection sites. PASSIVE EXPOSURE ## Can passive exposure to weed affect hair follicle test results? Passive exposure to marijuana smoke is unlikely to produce a positive hair follicle test result. Hair testing detects THC metabolites that are incorporated into the hair shaft from the bloodstream, not just surface contamination. Labs use washing procedures to remove external contaminants before analysis. Thus, incidental contact or secondhand smoke usually does not cause a positive result. TEST ACCURACY ## How accurate is a hair follicle test for detecting weed? Hair follicle testing is highly accurate for detecting marijuana use within the 90-day detection window. The test measures THC metabolites, providing objective evidence of drug consumption. AMH Nationwide partners with labs accredited by [SAMHSA](https://www.samhsa.gov/workplace/drug-testing), CAP, and CLIA, ensuring rigorous standards. All positive screens undergo Medical Review Officer confirmation, reducing false positives. ## Schedule a Hair Follicle Drug Test for Weed To arrange a hair follicle drug test for marijuana, contact AMH Nationwide. We provide lab orders and direct you to one of over 20,000 collection sites nationwide. Call (877) 731-6362 to speak with a representative. [Call (877) 731-6362](tel:+18777316362)[Contact Us](https://amhnationwide.com/contact-us/) WHO ORDERS ## Who typically requires hair follicle testing for weed? Employers, courts, [probation](https://amhnationwide.com/hair-follicle-drug-test-probation/) officers, and other legal entities commonly order hair follicle drug tests for marijuana. The extended detection window makes it suitable for monitoring past drug use over several months. Individuals may also request hair testing to verify abstinence or for personal reasons. AMH Nationwide facilitates testing through authorized lab networks. COMPARISON ## How does hair follicle testing compare to other drug tests for weed? Hair follicle tests detect marijuana use for up to 90 days, much longer than [urine](https://amhnationwide.com/urine-drug-testing/) or saliva tests, which detect use typically up to 3-30 days depending on frequency. Blood tests detect very recent use but have the shortest detection window. Hair testing cannot detect very recent use within the past week due to hair growth time. | Test Type | Detection Window for Weed | | --- | --- | | Hair Follicle Test | Up to 90 days | | Urine Test | 1-30 days depending on use | | Saliva Test | Up to 24-48 hours | | Blood Test | Up to 24 hours | 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 Hair follicle tests typically detect THC metabolites about 7 to 10 days after use, as it takes time for hair to grow out and incorporate the metabolites. Some hair treatments may reduce drug metabolite levels, but labs use sensitive methods and wash samples to minimize interference. Results remain reliable. No. DOT-regulated safety-sensitive testing requires federally certified urine testing under [49 CFR Part 40](https://www.transportation.gov/odapc/part40). Hair tests are for non-DOT roles. Yes. Heavier or frequent marijuana use generally results in higher metabolite levels, making detection more likely over the 90-day window. A small hair sample, about 1.5 inches long and the width of a pencil, is cut close to the scalp, usually from the crown area. No. AMH Nationwide provides the lab order and directs you to a collection site. There is no online ordering for hair follicle drug tests. 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-does-weed-stay-in-a-hair-follicle-test/