--- title: "How long can hair drug test go back" description: "Learn how long can hair drug test go back to detect drug use. Hair follicle tests detect months of drug history. Call (877) 731-6362 for lab testing info." author: "AMH Nationwide" date: "2026-08-28" tags: ["how long can hair drug test go back", "how long can hair drug test go back | how long can hair testing for drugs go back | how long can a hair follicle drug test go back | how long do drugs stay in your hair | how long do drugs stay in hair | how long will drugs stay in your hair | how long can a hair follicle test go back | how long do drugs stay in hair follicle | how long can drugs stay in your hair | how long do hair follicle drug test go back"] canonical: "https://amhnationwide.com/how-long-can-hair-drug-test-go-back/" last_updated: "2026-08-28" --- # How long can hair drug test go back **By AMH Nationwide** | August 28, 2026 Learn how long can hair drug test go back to detect drug use. Hair follicle tests detect months of drug history. Call (877) 731-6362 for lab testing info. --- How long can hair drug test go back depends on the length of hair sampled, typically up to 90 days or 3 months. Hair follicle drug tests detect drug metabolites embedded in hair shafts, providing a longer detection window than urine or saliva tests. Call (877) 731-6362 to schedule testing at nationwide collection sites. [DETECTION WINDOW](https://amhnationwide.com/hair-follicle-drug-test-detection-window/) ## How long can hair testing for drugs go back? Hair testing for drugs can typically go back about 90 days or 3 months, depending on the length of hair collected. Hair grows approximately half an inch per month, and standard testing uses 1.5 inches of hair closest to the scalp to detect drug use during that period. Longer hair samples can extend the detection window proportionally, but most labs limit samples to 1.5 inches due to standard protocols and accuracy considerations. TESTING PROCESS ## How does a hair follicle drug test detect drug use over time? A hair follicle drug test detects drug metabolites that enter the hair shaft from the bloodstream after drug use. As hair grows, these metabolites become trapped in the hair cortex, preserving a timeline of drug exposure. Because hair grows slowly, the test can show drug use history over months, unlike [urine](https://amhnationwide.com/urine-drug-testing/) or saliva tests that detect only recent use. The tested hair sample is collected at a designated collection site 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, and ExperTox. DRUGS DETECTED ## How long do drugs stay in your hair and which drugs can be detected? Drugs stay in hair follicles as long as the hair remains on the scalp, typically up to 90 days of growth. Common drugs detected include marijuana, cocaine, opiates, amphetamines, methamphetamines, PCP, and synthetic opioids. Hair tests detect metabolites, not the parent drug, which confirms actual drug use rather than environmental exposure. Marijuana (THC) detection: up to 90 days Cocaine detection: up to 90 days Opiates detection: up to 90 days Amphetamines detection: up to 90 days Methamphetamines detection: up to 90 days TESTING LIMITS ## Can hair drug tests detect one-time or passive drug exposure? Hair drug tests detect drug metabolites from actual ingestion, so one-time use may be detectable depending on timing and hair length. Passive exposure, such as environmental smoke, typically does not produce positive results because metabolites must enter the bloodstream to be incorporated into hair. Certified Medical Review Officers review every non-negative screen to ensure accurate interpretation. ## Schedule Your Hair Drug Test Today Call (877) 731-6362 to get lab orders and find a nearby collection site for hair follicle drug testing with comprehensive detection up to 90 days. [Call (877) 731-6362](tel:+18777316362)[Contact Us](https://amhnationwide.com/contact-us/) DOT REGULATIONS ## How long can hair follicle drug test go back for DOT-regulated testing? The Department of Transportation (DOT) requires urine drug testing under federally certified protocols ([49 CFR Part 40](https://www.transportation.gov/odapc/part40)) for safety-sensitive roles. Hair testing is not accepted for DOT-mandated tests but is used for non-DOT employment or legal testing. For non-DOT roles, hair testing offers a longer detection window, typically up to 90 days. ORDERING & COLLECTION ## How do I arrange a hair follicle drug test with AMH Nationwide? AMH Nationwide provides lab orders and directs the requester to one of 20,000+ nationwide collection sites. There is no online ordering. To arrange testing, call (877) 731-6362. The hair sample is collected by trained personnel and sent to one of five national labs for analysis. Results are reviewed by certified Medical Review Officers before reporting. 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 follicle drug tests generally detect drug use for up to 90 days or 3 months, based on hair length and growth rate. Yes, depending on the timing and hair sample length, a one-time drug use can be detected as metabolites incorporate into hair after ingestion. No, passive exposure usually does not produce positive results because drug metabolites must enter the bloodstream to be incorporated into hair. No, DOT regulations require urine testing under federal protocols. Hair tests are used for non-DOT testing. A small hair sample, typically 1.5 inches long, is cut close to the scalp by trained collectors at authorized collection sites. All non-negative hair drug test results are reviewed by certified Medical Review Officers to ensure accuracy before reporting. 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-can-hair-drug-test-go-back/