--- title: "How far back does a hair follicle go" description: "Learn how far back a hair follicle goes for drug testing. Understand detection windows and test reliability. Call (877) 731-6362 for lab collection info." author: "AMH Nationwide" date: "2026-08-28" tags: ["how far back does a hair follicle go"] canonical: "https://amhnationwide.com/how-far-back-does-a-hair-follicle-go/" last_updated: "2026-08-28" --- # How far back does a hair follicle go **By AMH Nationwide** | August 28, 2026 Learn how far back a hair follicle goes for drug testing. Understand detection windows and test reliability. Call (877) 731-6362 for lab collection info. --- How far back does a hair follicle go is a common question in drug testing. Hair follicle tests typically detect drug use up to 90 days prior to collection, reflecting approximately three months of history. This detection period depends on hair length and growth rates. Call (877) 731-6362 to schedule a collection or learn more. [DETECTION WINDOW](https://amhnationwide.com/hair-follicle-drug-test-detection-window/) ## How far back does a hair follicle go in drug testing? A hair follicle drug test can detect drug use approximately 90 days prior to the test date. This is because hair grows about half an inch per month, and standard testing analyzes the first 1.5 inches of hair closest to the scalp. This length captures roughly three months of drug exposure. The detection window depends on the length of the hair sample collected. Longer hair can extend the detection period, but most labs, including those used by AMH Nationwide, use up to 1.5 inches to maintain consistent detection windows. TESTING PROCESS ## How is the hair follicle sample collected and analyzed? Hair follicle samples are collected by cutting a small amount of hair close to the scalp, usually from the crown area. This ensures the newest hair growth is tested for the most recent 90-day period. AMH Nationwide routes hair samples through its 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 uses scientifically validated methods to extract drug metabolites from the hair shaft. All non-negative hair test results undergo review by a certified Medical Review Officer (MRO) to confirm accuracy and rule out potential false positives. WHO ORDERS ## Who typically orders hair follicle drug tests and why? Employers, courts, [probation](https://amhnationwide.com/hair-follicle-drug-test-probation/) officers, and individuals commonly order hair follicle drug testing to monitor long-term drug use. This test is preferred for its ability to detect consistent patterns over months rather than recent or one-time use. Hair testing is especially useful in non-DOT safety-sensitive roles because DOT regulations require federally certified [urine](https://amhnationwide.com/urine-drug-testing/) testing protocols. Hair tests provide an alternative for roles not regulated by DOT. SCIENCE OF DETECTION ## What scientific factors affect how far back a hair follicle can detect drug use? Hair grows at an average rate of about 0.5 inches per month, but this can vary by individual. The standard 1.5-inch hair sample covers approximately 90 days of growth. Drugs enter the hair follicle through the bloodstream and are deposited into the hair shaft as it forms. This process makes hair testing a reliable indicator of past drug exposure. External contamination and passive exposure are considered during analysis, and the labs follow strict protocols to differentiate between actual drug use and environmental exposure. ## Schedule a Hair Follicle Drug Test To arrange hair follicle testing through AMH Nationwide and access our network of over 20,000 collection sites, call (877) 731-6362. Our team will guide you through the process. [Call (877) 731-6362](tel:+18777316362)[Contact Us](https://amhnationwide.com/contact-us/) COMPARISON ## How does hair follicle testing compare to other drug testing methods? | Test Type | Detection Window | | --- | --- | | Urine Test | 1 to 7 days depending on the drug | | Blood Test | Hours to 1-2 days | | Saliva Test | 1 to 3 days | | Hair Follicle Test | Up to 90 days | Hair follicle tests offer the longest detection window compared to urine, blood, or saliva testing. This makes them ideal for assessing long-term drug use rather than recent consumption. LIMITATIONS ## Can hair follicle tests detect very recent drug use or one-time exposure? Hair follicle testing does not detect drug use within the past 5 to 7 days because the hair containing the drug metabolites has not yet grown above the scalp surface. One-time or very recent drug use may not be detected in hair tests, but repeated or chronic use is reliably identified. Attempting to evade or manipulate hair follicle tests is difficult due to laboratory protocols and MRO review. AMH Nationwide does not provide advice on evasion tactics. 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 Typically, 1.5 inches of hair closest to the scalp is collected, usually amounting to about 100 strands. This sample represents approximately 90 days of drug use history. Hair color and texture have minimal impact on drug detection in hair. Labs use standardized extraction methods to ensure accurate results regardless of hair type. Hair testing can detect certain alcohol metabolites like [ethyl glucuronide](https://amhnationwide.com/hair-etg-alcohol-test/) (EtG) but is less common than drug testing. AMH Nationwide can provide information on specific panels available. Results typically take 3 to 5 business days after the lab receives the sample. All positives are reviewed by a Medical Review Officer before final reporting. Hair treatments, bleaching, or dyeing can potentially reduce detectable drug levels but do not guarantee a negative result. Labs consider these factors during analysis. No. DOT regulations require urine testing under federally certified protocols. Hair follicle testing is used for non-DOT safety-sensitive roles. 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-a-hair-follicle-go/