--- title: "Will one hit of weed show up on hair test" description: "Will one hit of weed show up on hair test? Hair drug tests detect THC exposure over weeks. Understand detection details. Call (877) 731-6362 for testing info." author: "AMH Nationwide" date: "2026-08-28" tags: ["will one hit of weed show up on hair test"] canonical: "https://amhnationwide.com/will-one-hit-of-weed-show-up-on-hair-test/" last_updated: "2026-08-28" --- # Will one hit of weed show up on hair test **By AMH Nationwide** | August 28, 2026 Will one hit of weed show up on hair test? Hair drug tests detect THC exposure over weeks. Understand detection details. Call (877) 731-6362 for testing info. --- Will one hit of weed show up on hair test? Hair drug tests detect THC metabolites deposited in hair shafts, reflecting drug use over weeks to months. One-time or minimal exposure may not always be detectable, but hair testing is sensitive to repeated use. For accurate testing guidance, call (877) 731-6362. TEST BASICS ## What is a hair drug test and how does it detect THC? A hair drug test analyzes a small sample of hair to detect drug metabolites, including THC from marijuana use. When THC is consumed, it metabolizes and enters the bloodstream, eventually depositing in the hair follicles as hair grows. The test typically examines the most recent 1.5 inches of hair, representing approximately 90 days of drug exposure. Hair samples are collected following strict chain-of-custody protocols and 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. These labs use advanced techniques to identify THC metabolites, ensuring accurate and reliable results. DETECTION DETAILS ## Will one hit of weed show up on hair test? One hit of weed may not always produce detectable THC metabolite levels in hair. Hair testing is designed to detect repeated or chronic marijuana use rather than single or very low-level exposures. The sensitivity depends on several factors including hair type, amount of THC consumed, and individual metabolism. Since hair grows approximately 0.5 inches per month, the test detects drug use over a 90-day window. A single hit might deposit minimal THC in hair, sometimes below the lab’s cutoff threshold for a positive result. However, any non-negative screen will be reviewed by a certified Medical Review Officer as standard procedure. TESTING PROTOCOLS ## How reliable is hair testing for detecting occasional marijuana use? Hair testing is reliable for detecting repeated marijuana use but less sensitive for low-level or single-use exposure. The cutoff levels for THC metabolites are established to reduce false positives from environmental contamination or passive exposure. The five national lab networks used by AMH Nationwide follow [SAMHSA](https://www.samhsa.gov/workplace/drug-testing)-aligned guidelines and CLIA-certified processes to ensure accuracy. DOT-regulated safety-sensitive positions require federally certified [urine](https://amhnationwide.com/urine-drug-testing/) testing under [49 CFR Part 40](https://www.transportation.gov/odapc/part40); hair testing is primarily used for non-DOT roles. PASSIVE EXPOSURE ## Can passive exposure to marijuana cause a positive hair test? Passive exposure to marijuana smoke can result in trace amounts of THC on hair surfaces but usually does not lead to positive hair test results because labs wash hair samples before analysis to remove external contamination. The testing labs apply rigorous wash procedures and use metabolite detection rather than just THC presence to distinguish actual ingestion from environmental exposure. Therefore, passive exposure alone is unlikely to cause a confirmed positive hair test. ## Need Reliable Hair Drug Testing? Call (877) 731-6362 to arrange a hair drug test through AMH Nationwide. We connect you to national labs and certified collection sites with expert result review. [Call (877) 731-6362](tel:+18777316362)[Contact Us](https://amhnationwide.com/contact-us/) TEST ORDERING ## How do I get a hair drug test through AMH Nationwide? AMH Nationwide does not offer online ordering. To arrange a hair drug test, call (877) 731-6362 to speak with a representative who will provide a lab order and direct you to a nearby collection site among our nationwide network. Samples collected are sent to one of five national labs for processing. Results are reviewed by a certified Medical Review Officer to ensure accuracy and compliance with regulatory standards. Pricing varies by test panel and [detection window](https://amhnationwide.com/hair-follicle-drug-test-detection-window/); call for a quote. RESULTS AND REVIEW ## What happens if a hair test detects THC? If THC metabolites are detected, the initial screening is followed by confirmatory testing to validate the result. All non-negative results are reviewed by a certified Medical Review Officer (MRO) who evaluates medical explanations or prescriptions that might explain the findings. The MRO process ensures the final report is accurate and fair. Employers, courts, or [probation](https://amhnationwide.com/hair-follicle-drug-test-probation/) officers receive verified results that comply with regulatory and legal standards. 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 metabolites typically appear in hair about 5 to 10 days after use, as hair needs to grow out from the follicle. Hair testing reflects drug use over approximately 90 days. Yes, hair color, texture, and cosmetic treatments can influence THC metabolite incorporation. Darker or coarse hair may bind more drug metabolites, but labs account for variability during analysis. Hair tests detect longer-term use over months, while urine tests detect recent use within days to weeks. Hair tests are less useful for detecting very recent or single-use exposure. Synthetic cannabinoids require specialized testing panels. Standard hair tests for marijuana detect natural THC metabolites but may not detect synthetic variants without specific assays. Body hair can be collected for testing if head hair is unavailable, but detection windows and metabolite levels may vary. Discuss options when scheduling your test. Yes, hair tests are commonly used by employers, courts, and probation agencies to monitor drug use over extended periods, especially in non-DOT regulated roles. 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/will-one-hit-of-weed-show-up-on-hair-test/