--- title: "How far back can a hair test detect drugs" description: "Learn how far back a hair test can detect drugs with AMH Nationwide. Hair follicle drug testing detects past use up to 90 days. Call (877) 731-6362." author: "AMH Nationwide" date: "2026-08-28" tags: ["how far back can a hair test detect drugs", "how far back can a hair test detect drugs | how far back a hair follicle drug test | how far back hair follicle drug test | how far back hair follicle test | how far back do hair follicle drug test | how far back for hair drug test | how far back is a hair drug test | how far back can a hair follicle test detect drugs | how far back can a hair follicle drug test | how far back can a hair follicle test for drugs"] canonical: "https://amhnationwide.com/how-far-back-can-a-hair-test-detect-drugs/" last_updated: "2026-08-28" --- # How far back can a hair test detect drugs **By AMH Nationwide** | August 28, 2026 Learn how far back a hair test can detect drugs with AMH Nationwide. Hair follicle drug testing detects past use up to 90 days. Call (877) 731-6362. --- How far back can a hair test detect drugs? Hair drug testing can identify drug use typically up to 90 days prior to collection. This method analyzes hair follicles to reveal past substance use with high accuracy. AMH Nationwide directs collections to top labs and reviews all results with certified Medical Review Officers. Call (877) 731-6362. [DETECTION WINDOW](https://amhnationwide.com/hair-follicle-drug-test-detection-window/) ## How far back can a hair follicle drug test detect drugs? A hair follicle drug test can generally detect drug use for up to 90 days before the test date. This is because drugs and their metabolites become trapped in the hair shaft as it grows, providing a historical record of substance use. Hair grows approximately half an inch per month. Standard testing analyzes about 1.5 inches of hair closest to the scalp, covering roughly a three-month period. Typical detection window: up to 90 days Hair length tested: usually 1.5 inches from scalp Detection depends on hair growth rate and drug type TESTING PROCESS ## How does a hair follicle drug test work to detect past drug use? The hair follicle drug test works by analyzing the hair shaft for traces of drugs and their metabolites. When a person uses drugs, these substances enter the bloodstream and are deposited into the growing hair cells. As hair grows, these drug traces become part of the hair structure, allowing labs to detect past drug use over an extended period compared to [urine](https://amhnationwide.com/urine-drug-testing/) or saliva tests. LAB NETWORKS ## Which labs process hair follicle drug tests for AMH Nationwide? AMH Nationwide routes hair follicle drug test collections through five national lab networks: [Quest Diagnostics](https://www.questdiagnostics.com/), [LabCorp](https://www.labcorp.com/), Omega Labs, United States Drug Testing Labs, and ExperTox. Each lab follows strict protocols and submits all non-negative results for review by a certified Medical Review Officer to ensure accuracy and compliance. TEST LIMITATIONS ## Are there limitations to how far back a hair follicle test can detect drugs? While hair follicle tests can detect drug use up to 90 days prior, factors such as hair length, hair growth rate, and cosmetic treatments can affect results. Shorter hair or shaved heads may limit the detection window. Additionally, passive exposure to drugs does not typically produce a positive result under standard testing protocols. ## Need a Hair Follicle Drug Test? Contact AMH Nationwide Call (877) 731-6362 to schedule your hair follicle drug test through our national network of labs and collection sites. All results are reviewed by certified Medical Review Officers. [Call (877) 731-6362](tel:+18777316362)[Contact Us](https://amhnationwide.com/contact-us/) DOT & NON-DOT ## Can hair follicle drug tests be used for DOT-regulated safety-sensitive positions? Hair follicle drug tests are not approved for Department of Transportation (DOT) safety-sensitive roles. DOT regulations require urine testing using federally certified protocols under [49 CFR Part 40](https://www.transportation.gov/odapc/part40). Hair testing is available for non-DOT roles seeking extended detection windows beyond urine testing. ORDERING & COLLECTION ## How do I arrange a hair follicle drug test with AMH Nationwide? AMH Nationwide provides the lab order and directs the requester to one of over 20,000 nationwide collection sites. There is no online ordering; all test requests must be made by phone. To schedule a hair follicle drug test, call (877) 731-6362. Pricing varies by test panel and detection window. Contact us for a quote. 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 testing can detect drug use typically up to 90 days after consumption because drugs deposit in the hair shaft as it grows. Yes, hair tests can detect even a single use if enough drug metabolites are incorporated into the hair during growth. Hair color can have a minor effect on drug binding, but labs adjust for this. Hair testing remains reliable across different hair types. Hair tests detect drug use after about 7-10 days of hair growth post-exposure, so very recent use may not be immediately detectable. Hair tests provide a longer detection window but do not detect very recent drug use, unlike urine tests which detect recent exposure within days. Yes, employers can request hair follicle drug testing. AMH Nationwide provides lab orders and directs to collection sites. Call (877) 731-6362 to arrange testing. 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-back-can-a-hair-test-detect-drugs/