--- title: "How far back does gm hair test go" description: "Learn how far back does GM hair test go for drug detection. Understand timelines and reliability. Call (877) 731-6362 for lab testing info." author: "AMH Nationwide" date: "2026-08-28" tags: ["how far back does gm hair test go"] canonical: "https://amhnationwide.com/how-far-back-does-gm-hair-test-go/" last_updated: "2026-08-28" --- # How far back does gm hair test go **By AMH Nationwide** | August 28, 2026 Learn how far back does GM hair test go for drug detection. Understand timelines and reliability. Call (877) 731-6362 for lab testing info. --- How far back does GM hair test go is typically up to 90 days, as hair samples can reflect drug use from the past three months. The GM hair test analyzes segments of hair to detect drug metabolites embedded in the hair shaft. This method is reliable for detecting long-term drug use. Call (877) 731-6362 for testing details. [DETECTION WINDOW](https://amhnationwide.com/hair-follicle-drug-test-detection-window/) ## How far back does GM hair test go in detecting drug use? The GM hair test generally detects drug use up to 90 days prior to sample collection. Hair grows approximately 0.5 inches per month, and a standard 1.5-inch hair sample segment is analyzed, representing about three months of drug history. This test detects drug metabolites incorporated into the hair shaft from the bloodstream, making it effective for identifying long-term drug use rather than recent or one-time use. TESTING PROCESS ## What is the procedure for GM hair testing at AMH Nationwide? AMH Nationwide directs test requesters 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 for GM hair testing. There is no online ordering; all tests require a lab order from the requester. Hair samples are collected at approved collection sites and sent to the lab for analysis. All non-negative results undergo review by a certified Medical Review Officer (MRO) to ensure accuracy and proper interpretation. TEST SENSITIVITY ## How sensitive is the GM hair test for drug detection? The GM hair test is highly sensitive for detecting drug metabolites embedded in the hair shaft, including drugs like marijuana, cocaine, opiates, amphetamines, and PCP. The test can detect repeated or chronic drug use patterns within the 90-day detection window but is less effective for identifying very recent or single-use instances due to the time required for metabolites to incorporate into hair. COMPARISON ## How does the GM hair test detection window compare to other drug tests? | Test Type | Typical Detection Window | | --- | --- | | [Urine](https://amhnationwide.com/urine-drug-testing/) Drug Test | 1 to 7 days depending on drug | | Blood Drug Test | Hours to 1-2 days | | GM Hair Test | Up to 90 days | | Saliva Drug Test | 1 to 3 days | This comparison highlights the GM hair test’s advantage in detecting drug use over a longer period compared to urine, blood, or saliva tests. ## Need Accurate GM Hair Testing? Contact AMH Nationwide to schedule your GM hair test through one of our national lab networks. Call (877) 731-6362 for assistance. [Call (877) 731-6362](tel:+18777316362)[Contact Us](https://amhnationwide.com/contact-us/) DOT & NON-DOT USE ## Is the GM hair test used for DOT-regulated drug testing? The GM hair test is not used for DOT-regulated safety-sensitive positions. DOT requires federally certified urine testing under [49 CFR Part 40](https://www.transportation.gov/odapc/part40). Hair testing is typically used for non-DOT roles or situations where long-term drug use detection is necessary. ORDERING & COST ## How do I arrange a GM hair test and what affects the cost? To arrange a GM hair test, the requester must provide a lab order and contact AMH Nationwide to be directed to a collection site. Pricing varies depending on the drug panel selected and detection window required. Contact AMH Nationwide at (877) 731-6362 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 The GM hair test typically detects drug metabolites after about 7 to 10 days, as it takes time for the hair containing drug markers to grow above the scalp. A single use may be detected if it occurred several days before sample collection, but the test is more reliable for identifying repeated or chronic drug use. Hair color and type may minimally affect drug incorporation, but labs use validated methods to mitigate these variables ensuring accurate results. Passive exposure is unlikely to cause a positive GM hair test because drug metabolites must be incorporated internally into the hair from the bloodstream. Results from GM hair tests usually take 5 to 7 business days after the sample reaches the lab, including Medical Review Officer evaluation. The standard GM hair test focuses on drugs; specific alcohol biomarkers require separate hair testing panels not included in routine drug screening. 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-does-gm-hair-test-go/