--- title: "How long does a hair sample drug test go back" description: "How long does a hair sample drug test go back? Hair testing can detect drug 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 a hair sample drug test go back", "how long does a hair sample drug test go back | how long does hair sample drug test go back"] canonical: "https://amhnationwide.com/how-long-does-a-hair-sample-drug-test-go-back/" last_updated: "2026-08-28" --- # How long does a hair sample drug test go back **By AMH Nationwide** | August 28, 2026 How long does a hair sample drug test go back? Hair testing can detect drug use up to 90 days. Call (877) 731-6362 for lab testing info and scheduling. --- How long does a hair sample drug test go back? A hair sample drug test typically detects drug use up to 90 days prior to collection. This method provides a longer detection window than urine or saliva tests. AMH Nationwide routes collections through five national labs with results reviewed by a certified Medical Review Officer. Call (877) 731-6362. [DETECTION WINDOW](https://amhnationwide.com/hair-follicle-drug-test-detection-window/) ## How long does a hair sample drug test go back? A hair sample drug test generally goes back up to 90 days, sometimes slightly longer depending on hair length. Drugs are deposited in the hair shaft from the bloodstream and remain detectable as hair grows approximately 0.5 inches per month. Standard hair drug tests analyze about 1.5 inches of hair, representing roughly a three-month period of drug use. This detection window is significantly longer than [urine](https://amhnationwide.com/urine-drug-testing/) or saliva tests, which typically detect recent use within days. Average detection window: 90 days Hair growth rate: ~0.5 inches per month Standard sample length: 1.5 inches Longer window than urine or saliva tests Because hair testing reflects drug intake over weeks to months, it is often used in employment, legal, and [probation](https://amhnationwide.com/hair-follicle-drug-test-probation/) settings where a longer history is relevant. TESTING PROCESS ## What is the process for collecting and testing a hair sample for drugs? Collection involves cutting a small hair sample close to the scalp, usually from the crown. 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. AMH Nationwide coordinates the lab order and directs the requester to a collection site. The labs use advanced techniques to extract and analyze drug metabolites from the hair. Every non-negative result undergoes review by a certified Medical Review Officer to confirm validity and rule out potential confounding factors. Sample collected near scalp Sent to one of five national labs Analyzed for drug metabolites Non-negative results reviewed by Medical Review Officer This standardized process ensures accuracy and compliance with industry regulations, including [SAMHSA](https://www.samhsa.gov/workplace/drug-testing) and DOT guidelines where applicable. APPLICATIONS ## Who typically orders hair sample drug tests and why? Hair drug tests are commonly ordered by employers, courts, probation officers, and individuals requiring a longer detection window than urine or saliva testing can provide. They are particularly useful for safety-sensitive positions not regulated by DOT, as DOT requires federally certified urine testing protocols. Hair tests help verify abstinence or detect patterns of drug use over months. Employers screening for long-term drug use Courts and probation monitoring compliance Individuals seeking extended detection windows Non-DOT safety-sensitive roles Because hair tests provide historical data rather than recent use, they are often used when a broader assessment of drug use history is needed. DRUGS DETECTED ## What drugs can a hair sample drug test detect? Hair drug tests can detect a wide range of substances including marijuana, cocaine, opiates, amphetamines, methamphetamines, phencyclidine (PCP), and synthetic opioids. The detection window and sensitivity depend on the drug’s incorporation into hair and the testing panel selected. AMH Nationwide offers various panels routed through accredited labs to meet specific testing needs. Marijuana (THC) Cocaine Opiates (heroin, morphine) Amphetamines and methamphetamines PCP Synthetic opioids Test panels can be customized based on employer or legal requirements, with prices varying accordingly. Call for a quote. ## Schedule a Hair Sample Drug Test Today Contact AMH Nationwide to arrange hair drug testing through one of our five national lab networks. Call (877) 731-6362 to speak with a representative and find a collection site near you. [Call (877) 731-6362](tel:+18777316362)[Contact Us](https://amhnationwide.com/contact-us/) LIMITATIONS ## Are there limitations or factors that affect how long hair drug tests go back? While hair testing can detect drug use up to 90 days, factors such as hair length, hair color, and cosmetic treatments (bleaching, dyeing) can affect results. Very short hair or shaved heads may limit the detection window. Passive exposure to drugs is unlikely to produce a positive hair test due to the incorporation mechanism. The test cannot determine exact timing within the detection window. Hair length limits detection window Cosmetic treatments may reduce detectability Passive exposure unlikely to cause positives Cannot pinpoint exact date of use Understanding these factors helps interpret hair test results accurately in workplace or legal contexts. DOT AND HAIR TESTING ## Can hair sample drug tests be used for DOT-regulated safety-sensitive positions? Hair sample drug tests are not accepted for Department of Transportation (DOT)-regulated safety-sensitive testing. DOT requires urine drug tests conducted under the federally certified protocol outlined in [49 CFR Part 40](https://www.transportation.gov/odapc/part40). Hair testing is accepted for non-DOT safety-sensitive positions where a longer detection window is desired. Employers must follow DOT regulations for applicable roles and use hair testing only where compliant. DOT requires federally certified urine testing Hair tests not accepted for DOT safety-sensitive roles Hair tests used for non-DOT safety-sensitive positions AMH Nationwide ensures compliance by routing tests appropriately and advising on protocol requirements. 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 drug tests typically detect drug use up to 90 days prior to collection, depending on hair length and growth rate. Hair tests are less effective for very recent use within the past few days; urine or saliva tests are better for detecting recent intake. Some studies suggest darker hair may incorporate drugs more readily, but labs account for variability to maintain accuracy. Yes, bleaching or dyeing hair can reduce drug metabolite levels and potentially affect test sensitivity. No, DOT requires urine testing under federally certified protocols; hair testing is not accepted for these roles. All non-negative results are reviewed by a certified Medical Review Officer to confirm validity and rule out alternative explanations. 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-a-hair-sample-drug-test-go-back/