--- title: "How far does a hair drug test go" description: "How far does a hair drug test go? It typically detects drug use up to 90 days prior. Understand hair follicle testing from AMH Nationwide. Call (877) 731-6362." author: "AMH Nationwide" date: "2026-08-28" tags: ["how far does a hair drug test go", "how far does a hair drug test go | how far does a hair follicle test go | how far does hair drug test go | how far does the hair drug testing go | how far does a hair follicle drug test go"] canonical: "https://amhnationwide.com/how-far-does-a-hair-drug-test-go/" last_updated: "2026-08-28" --- # How far does a hair drug test go **By AMH Nationwide** | August 28, 2026 How far does a hair drug test go? It typically detects drug use up to 90 days prior. Understand hair follicle testing from AMH Nationwide. Call (877) 731-6362. --- How far does a hair drug test go? Hair drug tests generally detect drug use within a 90-day period prior to collection. This test analyzes hair follicles to provide a reliable history of substance intake. AMH Nationwide uses certified labs and Medical Review Officers to ensure accurate results. Call (877) 731-6362 for testing details. [DETECTION WINDOW](https://amhnationwide.com/hair-follicle-drug-test-detection-window/) ## How far back can a hair drug test detect drug use? A hair drug test can detect drug use for approximately 90 days prior to the sample collection. Hair grows at an average rate of about half an inch per month, and standard testing analyzes a 1.5-inch hair segment closest to the scalp. This allows for a three-month detection window, making it useful for identifying long-term drug use patterns rather than recent or one-time use. The test detects drug metabolites deposited in the hair shaft from bloodstream exposure after drug ingestion. Because hair preserves these metabolites over time, the test is less susceptible to short-term fluctuations or attempts to mask drug use compared to [urine](https://amhnationwide.com/urine-drug-testing/) or saliva testing. Typical detection window: up to 90 days Hair length analyzed: approximately 1.5 inches from scalp Detects metabolites incorporated into hair shaft Not effective for use within 7 days prior to collection Hair drug testing is commonly used by employers, courts, and [probation](https://amhnationwide.com/hair-follicle-drug-test-probation/) agencies to assess sustained drug use history rather than immediate intoxication. TESTING PROCESS ## How does a hair follicle drug test work? 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 AMH Nationwide’s 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 labs use advanced techniques such as immunoassay screening followed by confirmatory testing with gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS). Every non-negative screen is reviewed by a certified Medical Review Officer to ensure accuracy and rule out false positives. This process ensures a highly reliable and scientifically validated result that reflects drug use over the previous three months. Hair testing is not influenced by recent food or drink intake and is difficult to adulterate. Sample size: 90-120 strands of hair Laboratory techniques: immunoassay screening, GC-MS, LC-MS/MS Review: Certified Medical Review Officer evaluates all non-negative results Labs used: Quest Diagnostics, LabCorp, Omega Labs, United States Drug Testing Labs, ExperTox Because hair testing detects metabolites embedded in the hair shaft, external contamination or passive exposure rarely causes a positive result. APPLICATIONS ## Who orders hair follicle drug tests and why? Hair follicle drug tests are ordered by employers, courts, probation and parole officers, and individuals for various purposes. Employers use hair testing to screen for long-term drug use during [pre-employment](https://amhnationwide.com/pre-employment-hair-testing/) or random testing programs, especially for safety-sensitive roles not regulated by DOT. Courts and probation agencies rely on hair tests to monitor compliance with drug-related orders over extended periods. Individuals may request hair testing for personal knowledge or legal matters. Hair testing is favored when a longer detection window is needed compared to urine or saliva tests, providing a more comprehensive view of drug use history. Employers: pre-employment and random testing Courts and probation: compliance monitoring Individuals: personal or legal reasons Preferred for long-term detection over urine or saliva DOT-regulated safety-sensitive testing requires federally certified urine testing protocols; hair testing is not accepted for DOT roles. LIMITATIONS ## What are the limitations of hair drug testing? Hair drug testing does not detect very recent drug use within about 5 to 7 days because it takes time for drug metabolites to incorporate into the hair shaft above the scalp. Therefore, it cannot reliably identify use in the days immediately before collection. The test may be less effective if the individual has very short hair or shaves the head, as insufficient hair length can limit the sample. Certain hair treatments like bleaching or dyeing can reduce metabolite concentrations but do not invalidate the test. Laboratories adjust analysis protocols accordingly. Additionally, hair testing does not provide information about the exact timing or quantity of drug use, only that use occurred within the detection window. Cannot detect use within 5-7 days prior to test Limited by hair length or absence of hair Hair treatments may affect results but do not invalidate Does not specify exact timing or amount of drug use For recent drug use detection, urine or saliva tests are more appropriate. ## Need a Hair Drug Test? Contact AMH Nationwide For accurate hair drug testing with certified labs and Medical Review Officer oversight, call (877) 731-6362 to arrange your test today. [Call (877) 731-6362](tel:+18777316362)[Contact Us](https://amhnationwide.com/contact-us/) PASSIVE EXPOSURE ## Can passive exposure cause a positive hair drug test? Passive exposure to drugs, such as being in a room with smoke, is unlikely to cause a positive hair drug test. The test detects drug metabolites incorporated internally into the hair shaft from the bloodstream, not external contamination. Laboratories perform thorough washing procedures on hair samples to remove external contaminants before analysis. The certified Medical Review Officer also reviews non-negative results to consider possible environmental contamination and confirm drug use. Thus, hair drug testing is a reliable indicator of actual drug ingestion rather than passive exposure. Detects internal metabolites, not surface contamination Lab washing removes external contaminants Medical Review Officer reviews for environmental factors Positive results indicate drug use, not passive exposure This makes hair testing a preferred method when avoiding false positives from environmental exposure is important. HOW TO GET TESTED ## How do I arrange a hair drug test with AMH Nationwide? AMH Nationwide facilitates hair drug testing by providing lab orders and directing clients to one of over 20,000 nationwide collection sites. We do not offer online ordering; all test requests must be made by phone or through direct contact. To arrange testing, call (877) 731-6362 to discuss the appropriate test panel and detection window. Pricing varies based on the panel selected and detection window required, so call for a personalized quote. Once the lab order is issued, the client visits a collection site for hair sample collection. The sample is then sent to one of AMH’s five national lab networks for analysis. Results are reviewed by a certified Medical Review Officer and securely reported to the requester. Call (877) 731-6362 to request a test No online ordering available Choose test panel based on detection needs Visit a local collection site for sample Labs: Quest Diagnostics, LabCorp, Omega Labs, United States Drug Testing Labs, ExperTox Contact AMH Nationwide for expert guidance on hair drug testing options and scheduling. 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 must be at least 1.5 inches in length from the scalp to provide a 90-day detection window. Shorter hair may reduce detection time or require alternative testing. Chemical treatments like bleaching or dyeing can reduce drug metabolite levels but do not invalidate the test. Labs adjust analysis to account for treated hair. No. DOT-regulated safety-sensitive testing requires federally certified urine testing protocols under [49 CFR Part 40](https://www.transportation.gov/odapc/part40). Hair testing is used for non-DOT roles. Hair testing provides a longer detection window and is less susceptible to adulteration. Urine testing detects recent use but has a shorter detection period. Yes, if the use occurred within the detection window and sufficient metabolites incorporated into hair. However, very recent or single use close to test date may not be detected. Hair tests commonly detect substances like marijuana, cocaine, opiates, methamphetamine, PCP, and others depending on the test panel selected. 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-far-does-a-hair-drug-test-go/