--- title: "How long does weed stay in your system hair test" description: "Learn how long does weed stay in your system hair test detects THC. Understand detection windows and testing facts. Call (877) 731-6362 for lab testing info." author: "AMH Nationwide" date: "2026-08-28" tags: ["how long does weed stay in your system hair test"] canonical: "https://amhnationwide.com/how-long-does-weed-stay-in-your-system-hair-test/" last_updated: "2026-08-28" --- # How long does weed stay in your system hair test **By AMH Nationwide** | August 28, 2026 Learn how long does weed stay in your system hair test detects THC. Understand detection windows and testing facts. Call (877) 731-6362 for lab testing info. --- How long does weed stay in your system hair test? Hair follicle testing can detect THC exposure for up to 90 days, making it a reliable method for long-term drug use verification. This test is used by employers, courts, and probation agencies. Call (877) 731-6362 for more information on hair drug testing procedures and scheduling. TEST BASICS ## What is a hair drug test for weed and how does it work? A hair drug test for weed detects the presence of THC metabolites embedded in the hair shaft. When cannabis is consumed, THC enters the bloodstream and is deposited in growing hair follicles. This makes hair testing effective for identifying drug use over a longer period compared to [urine](https://amhnationwide.com/urine-drug-testing/) or saliva tests. The collection involves cutting a small sample of hair close to the scalp. The sample is then 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. AMH Nationwide coordinates the lab order and directs you to a local collection site. No online ordering is available. Call (877) 731-6362 to arrange testing. [DETECTION WINDOW](https://amhnationwide.com/hair-follicle-drug-test-detection-window/) ## How long does weed stay in your system hair test detect THC? Hair follicle tests can detect THC use for up to 90 days after consumption. The detection window depends on hair length since hair grows approximately 0.5 inches per month, and labs typically test 1.5 inches of hair from the scalp to cover the past three months. One-time or occasional use of weed can be detected within this 90-day window, although very light or infrequent use might produce lower concentrations of THC metabolites. Passive exposure to cannabis smoke is unlikely to produce a positive hair test because the metabolites must be incorporated into the hair follicle, not just deposited on the hair surface. TESTING PROCEDURE ## Who orders hair drug tests for weed and what is the collection process? Hair drug tests for weed are commonly ordered by employers, courts, [probation](https://amhnationwide.com/hair-follicle-drug-test-probation/) agencies, and individual clients requiring long-term drug use verification. The collection involves cutting approximately 1.5 inches of hair from close to the scalp, usually from the crown or back of the head. If head hair is unavailable, body hair may be used but with shorter detection windows and less standardization. AMH Nationwide facilitates the lab order and directs you to a nearby collection site within a national network of labs. Call (877) 731-6362 to schedule your test. LAB PROCESSING ## How do labs analyze hair samples for THC? Once the hair sample arrives at the lab, it undergoes a two-step process: an initial immunoassay screen followed by a confirmatory test using gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS) if the screen is positive. Every non-negative hair test result is reviewed by a certified Medical Review Officer (MRO) to ensure accuracy and to allow for legitimate medical explanations before a final report is issued. AMH Nationwide uses five nationally recognized labs, ensuring compliance with [SAMHSA](https://www.samhsa.gov/workplace/drug-testing), CAP, and CLIA standards for reliable results. ## Schedule Your Hair Drug Test for Weed Today To arrange a hair drug test for weed or discuss testing options, call AMH Nationwide at (877) 731-6362. We will direct you to a local collection site within our national lab network. [Call (877) 731-6362](tel:+18777316362)[Contact Us](https://amhnationwide.com/contact-us/) TEST ACCURACY ## Can hair drug tests for weed be beaten or produce false positives? Hair drug tests are highly accurate due to the confirmatory testing and MRO review process. Attempts to cheat or alter hair samples are generally ineffective because the test detects metabolites inside the hair shaft, not surface contamination. False positives are rare but can occur. That is why every non-negative screen is verified by a Medical Review Officer who reviews medications and medical history. Hair tests do not detect very recent use (within the past 7 days) because it takes time for THC metabolites to be incorporated into hair. OTHER CONSIDERATIONS ## What factors affect how long weed stays in your system hair test? Several factors influence detection times including hair length, hair color, rate of hair growth, frequency of use, and individual metabolism. External contamination is minimized by lab washing protocols before analysis, reducing the chance of environmental THC affecting results. Hair tests are 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). Hair testing is typically reserved for non-DOT roles. 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 tests generally cannot detect THC until about 7 days after use because it takes time for metabolites to grow into the hair shaft. Passive exposure is unlikely to cause a positive hair test because the test detects metabolites incorporated into the hair follicle, not surface contamination. Hair tests detect THC for up to 90 days, whereas urine tests typically detect recent use within 3 to 30 days depending on frequency and amount. If head hair is too short, body hair may be used, but detection windows may be shorter and less standardized. Yes, hair drug tests are widely accepted by employers, courts, and probation agencies for long-term drug use verification. AMH Nationwide arranges the lab order and directs you to a nearby collection site within a national lab network. Call (877) 731-6362 to schedule. 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-your-system-hair-test/