How long hair test weed
How Long Hair Test Weed Detects THC Use for Reliable Results
How long hair test weed detects THC depends on hair length and usage, typically up to 90 days. Hair testing provides a longer detection window than urine or saliva. AMH Nationwide routes collections through five national labs and reviews all results by certified Medical Review Officers. Call (877) 731-6362 for collection site information.
How long does a hair test detect weed use?
A hair test for weed typically detects THC use for up to 90 days, depending on hair length. Hair grows approximately 0.5 inches per month, so a standard 1.5-inch hair sample represents about a three-month detection window.
This detection period is much longer than urine or saliva tests, which detect recent use within days or weeks. Hair testing captures drug metabolites deposited in the hair shaft from the bloodstream.
How is a hair test for weed collected and analyzed?
Hair collection is performed at a designated site selected by AMH Nationwide, which coordinates with one of five national lab networks: Quest Diagnostics, LabCorp, Omega Labs, United States Drug Testing Labs, or ExperTox.
A small sample of hair, usually from the crown of the head, is cut close to the scalp. The sample is sent to the lab for testing, where sensitive instruments detect THC metabolites within the hair shaft.
All positive or non-negative results undergo review by a certified Medical Review Officer (MRO) to verify accuracy and rule out alternative explanations.
Can a hair test detect one-time or infrequent weed use?
Hair tests can detect one-time or infrequent THC use, but the amount of drug incorporated into hair is generally lower than with frequent use. Very low levels may not always be detected, depending on the sensitivity of the test panel.
Repeated or heavy use results in higher metabolite concentrations, increasing the likelihood of detection. Hair testing is more reliable for identifying patterns of use over weeks to months.
Can passive weed exposure cause a positive hair test?
Passive exposure to marijuana smoke is unlikely to cause a positive hair test. Hair testing detects metabolites formed inside the body after THC ingestion, not just external contamination.
Labs follow strict washing protocols to remove external contaminants from hair samples before analysis, reducing false positives caused by environmental exposure.
Need a Hair Test for Weed?
Contact AMH Nationwide to obtain a lab order and find a collection site near you. Call (877) 731-6362 for assistance.
How accurate and reliable is hair testing for weed?
Hair testing for THC is highly accurate when performed by accredited labs following SAMHSA guidelines. AMH Nationwide uses labs certified under CAP and CLIA, ensuring standardized procedures and quality control.
Results are reviewed by certified Medical Review Officers to confirm validity. This process minimizes false positives and false negatives for workplace, probation, or court-ordered testing.
What testing options does AMH Nationwide provide for hair drug tests?
AMH Nationwide offers hair testing routed through five national lab networks, with collection sites nationwide. We do not offer online ordering; instead, we provide lab orders and direct clients to collection locations.
For DOT-regulated safety-sensitive positions, federally certified urine tests under 49 CFR Part 40 are required. Hair testing is suitable for non-DOT roles seeking longer detection windows.
Common Questions
THC can be detected in hair for up to 90 days, while urine tests typically detect use within 3 to 30 days depending on frequency. Hair testing provides a longer detection window.
Hair color may influence drug incorporation slightly, but accredited labs adjust for this. Testing protocols and MRO review ensure accurate interpretation regardless of hair color.
Chemical treatments may reduce drug concentrations in hair but usually do not prevent detection. Labs consider this during analysis and MRO review.
Hair collection is non-invasive and painless. A small hair sample is cut close to the scalp, typically from the crown area.
AMH Nationwide does not offer at-home collection. Hair tests require lab orders and must be collected at authorized sites connected to national lab networks.
Results usually take several days to a week after sample collection, depending on the lab. All results are reviewed by a Medical Review Officer before release.
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.