How long does weed last in hair
How Long Does Weed Last in Hair for Reliable THC Detection
How long does weed last in hair depends on the detection window of the hair follicle test, which can detect THC up to 90 days after use. This test analyzes hair samples collected at certified labs, ensuring accurate results reviewed by Medical Review Officers. Call (877) 731-6362 to schedule your collection.
How long does weed last in hair after use?
Weed, or THC, can be detected in hair samples for up to 90 days after consumption. Hair drug testing analyzes the metabolites of THC that are deposited in the hair shaft as it grows. Because hair grows approximately 0.5 inches per month, a standard 1.5-inch hair sample represents roughly a 90-day detection window. This makes hair testing useful for identifying past marijuana use over a longer period compared to urine or saliva tests.
Detection beyond 90 days is uncommon because hair segments grow out and are cut off. However, the exact detection time can vary based on individual hair growth rates and testing protocols.
What is the hair drug test process for detecting THC?
Hair drug testing for THC involves collecting a small hair sample from the scalp, typically from the crown area. The sample is then sent to one of AMH Nationwide’s five national lab networks—Quest Diagnostics, LabCorp, Omega Labs, United States Drug Testing Labs, or ExperTox—for analysis. The labs test for THC metabolites incorporated into the hair shaft. Every non-negative result undergoes review by a certified Medical Review Officer (MRO) to confirm accuracy and rule out potential false positives.
AMH Nationwide directs the requester to a collection site; there is no online ordering. Contact us at (877) 731-6362 to arrange testing.
How long does THC last in hair compared to other testing methods?
THC detection time in hair is significantly longer than in urine or saliva. Urine tests typically detect THC from 3 to 30 days depending on usage frequency, while saliva tests detect recent use within hours to days. Hair testing can detect THC metabolites for up to 90 days, providing a longer retrospective window. This makes hair testing suitable for employers, courts, or probation officers who need a longer-term drug use history.
| Test Type | Typical THC Detection Window |
|---|---|
| Hair Test | Up to 90 days |
| Urine Test | 3 to 30 days |
| Saliva Test | Hours to a few days |
Can one-time use or passive exposure affect hair test results?
A single use of weed may be detected in hair if the THC metabolites are deposited in the hair shaft. However, detection depends on the amount consumed and hair growth timing. Passive exposure to marijuana smoke is unlikely to cause a positive hair test because the test detects metabolites from ingestion, not external contamination. Labs use wash procedures to remove external contaminants. The review by a Medical Review Officer further validates positive results to minimize false positives.
Schedule Your Hair Drug Test for Weed Today
Contact AMH Nationwide at (877) 731-6362 to arrange hair testing with certified labs and Medical Review Officer review. Get accurate THC detection up to 90 days.
Is hair testing for weed used in DOT-regulated safety-sensitive roles?
Hair testing for THC is not used for Department of Transportation (DOT) regulated safety-sensitive positions. DOT requires urine testing following the federally certified urine protocol under 49 CFR Part 40. Hair testing is accepted for non-DOT roles to provide a longer detection window. Employers who require DOT testing must follow the urine test regulations, while hair testing can be used for other employment or legal purposes.
How do I get a hair drug test for weed and what does it cost?
To get a hair drug test for weed through AMH Nationwide, you must call (877) 731-6362 to arrange a lab order and be directed to a nearby collection site. AMH does not provide online ordering. Pricing varies depending on the test panel and detection window required. Call to request a personalized quote based on your testing needs. All tests are processed at national labs with certified Medical Review Officer oversight for reliable results.
Common Questions
Typically, a 1.5-inch hair sample weighing about 100 milligrams is collected from the scalp to provide a 90-day detection window for THC metabolites.
Hair treatments like dyeing or bleaching may reduce THC metabolite levels, but labs have methods to detect and account for treated hair to ensure accurate results.
Hair testing provides a longer detection window and is less susceptible to adulteration, making it more reliable for detecting past marijuana use over months compared to urine testing.
Results typically take 3 to 5 business days after the lab receives the hair sample. Time may vary depending on the lab and test panel.
Hair drug testing can technically be performed on children, but testing minors usually requires legal consent and clear justification due to privacy and ethical considerations.
No, DOT regulations require urine testing for marijuana. AMH provides hair testing for non-DOT purposes only, following all federal guidelines.
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.