--- title: "What do hair follicles test for" description: "What do hair follicles test for? Hair follicle tests detect various drugs over 90 days. Get reliable results. Call (877) 731-6362 to schedule testing." author: "AMH Nationwide" date: "2026-08-28" tags: ["what do hair follicles test for", "what do hair follicles test for | what drugs do hair follicles test for"] canonical: "https://amhnationwide.com/what-do-hair-follicles-test-for/" last_updated: "2026-08-28" --- # What do hair follicles test for **By AMH Nationwide** | August 28, 2026 What do hair follicles test for? Hair follicle tests detect various drugs over 90 days. Get reliable results. Call (877) 731-6362 to schedule testing. --- What do hair follicles test for? Hair follicle tests detect drug metabolites deposited in hair strands, identifying drug use up to 90 days prior. They reveal substances such as cocaine, marijuana, opiates, amphetamines, and PCP. This method provides a longer detection window than urine tests and is used by employers and courts. Call (877) 731-6362 to arrange testing. OVERVIEW ## What do hair follicles test for? Hair follicle tests detect drug metabolites embedded in the hair shaft, providing a historical record of drug use. The primary substances tested include cocaine, marijuana (THC), opiates (such as heroin and morphine), amphetamines, methamphetamines, and phencyclidine (PCP). Hair follicle testing is valued for its longer [detection window](https://amhnationwide.com/hair-follicle-drug-test-detection-window/) compared to [urine](https://amhnationwide.com/urine-drug-testing/) or saliva tests, typically identifying drug use within the past 90 days. This makes it useful for employers, courts, and [probation](https://amhnationwide.com/hair-follicle-drug-test-probation/) officers who require evidence of longer-term patterns of substance use. Common drugs detected: cocaine, marijuana (THC), opiates, amphetamines, methamphetamines, PCP Detection window: up to 90 days from collection Method: metabolites deposited in hair shaft Use cases: employment screening, legal and probation monitoring TESTING PROCESS ## How is a hair follicle test performed? A small sample of hair, usually about 1.5 inches long and the width of a pencil, is collected close to the scalp. This sample represents roughly 90 days of hair growth and drug exposure. The sample is sent to one of AMH Nationwide’s five national lab partners: [Quest Diagnostics](https://www.questdiagnostics.com/), [LabCorp](https://www.labcorp.com/), Omega Labs, United States Drug Testing Labs, or ExperTox. Each lab analyzes the hair for drug metabolites using validated scientific methods. Non-negative results undergo review by a certified Medical Review Officer (MRO) to confirm findings and rule out legitimate medical explanations. Hair sample length approximately 1.5 inches Collection done at authorized collection sites nationwide Testing performed by nationally recognized labs Certified Medical Review Officer reviews all non-negative results DRUGS DETECTED ## What drugs do hair follicles test for? Hair follicle testing detects a range of commonly abused substances. The standard testing panels typically include: cocaine, marijuana (THC), opiates (including heroin, codeine, morphine), amphetamines (including methamphetamine), and phencyclidine (PCP). Some labs offer expanded panels that may include benzodiazepines, barbiturates, MDMA (ecstasy), or synthetic cannabinoids, but these are less common and require specific requests. Hair follicle tests measure drug metabolites, which are chemical byproducts formed when the body processes drugs, making the test highly reliable for confirming actual drug use rather than external contamination. Cocaine and its metabolites THC from marijuana Opiates: heroin, morphine, codeine Amphetamines and methamphetamines Phencyclidine (PCP) Contact AMH Nationwide to discuss specific drug panel options. Call (877) 731-6362 for details. DETECTION WINDOW ## How long do hair follicle tests detect drug use? Hair follicle tests typically detect drug use for up to 90 days prior to sample collection, depending on hair length and growth rate. This is significantly longer than urine tests, which usually detect recent drug use within days to weeks. The detection window begins roughly 7-10 days after drug ingestion, as it takes time for metabolites to be incorporated into new hair growth. Therefore, hair tests do not detect very recent drug use within the past week. Because hair grows approximately 0.5 inches per month, a 1.5-inch hair sample can provide a 90-day history of drug exposure. Longer hair samples may extend detection further but are less commonly used for standard testing. Detection window: up to 90 days Hair growth rate: about 0.5 inches per month No detection of drug use within past 7-10 days Longer detection than urine or saliva tests ## Schedule a Hair Follicle Drug Test Today To arrange hair follicle testing through AMH Nationwide and one of our five national lab networks, call (877) 731-6362. Our staff will direct you to a nearby collection site and explain the next steps. [Call (877) 731-6362](tel:+18777316362)[Contact Us](https://amhnationwide.com/contact-us/) TESTING RELIABILITY ## Can hair follicle tests be affected by passive exposure or external contamination? Hair follicle tests measure drug metabolites inside the hair shaft, which requires ingestion and metabolism of the drug. This significantly reduces the chance of false positives from passive exposure to drug smoke or environmental contamination. Labs use washing procedures to remove external contaminants before analysis. Additionally, the presence of metabolites rather than parent drugs indicates actual drug use. Because of these scientific safeguards, hair follicle testing is considered highly reliable and resistant to attempts to cheat or evade detection through external means. Measures metabolites inside hair shaft, not surface contamination Lab washing removes external contaminants High specificity reduces false positives from passive exposure Certified MRO review confirms results USE CASES ## Who uses hair follicle drug testing and why? Hair follicle drug testing is commonly used by employers for [pre-employment](https://amhnationwide.com/pre-employment-hair-testing/) screening and ongoing workforce testing, especially when a longer drug use history is needed. Courts and probation departments use hair testing to monitor compliance with drug-free conditions over extended periods. Individuals may also request hair follicle tests for personal reasons or legal matters. DOT-regulated safety-sensitive positions require federally certified urine testing under [49 CFR Part 40](https://www.transportation.gov/odapc/part40); hair testing is used for non-DOT roles only. Employers screening for long-term drug use Courts and probation monitoring Individual drug use verification Non-DOT safety-sensitive job testing 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, about 1.5 inches of hair closest to the scalp is collected, roughly the width of a pencil. This length covers approximately 90 days of drug use history. Standard hair follicle drug tests do not detect alcohol. Separate specialized tests are required to detect alcohol metabolites in hair. Hair color and type can slightly influence drug incorporation, but labs use scientifically validated methods to ensure accurate and consistent results regardless of hair characteristics. Results from hair follicle testing typically take 3 to 5 business days after the lab receives the sample. Non-negative results undergo additional review by a Medical Review Officer. Yes, hair follicle tests can detect even single instances of drug use since metabolites are deposited during hair growth, but detection depends on timing and hair length. No, DOT-regulated safety-sensitive testing requires federally certified urine testing under 49 CFR Part 40. Hair follicle testing is used for non-DOT roles only. 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/what-do-hair-follicles-test-for/