How long can thc be detected in hair
How Long Can THC Be Detected in Hair for Reliable Cannabis Testing
How long can THC be detected in hair depends on hair length and usage but typically up to 90 days or longer. Hair drug testing is a reliable method for detecting cannabis use over extended periods. AMH Nationwide processes hair samples through five national lab networks with certified Medical Review Officers reviewing all results. Call (877) 731-6362 for testing details.
How long can THC be detected in hair?
THC can be detected in hair for approximately 90 days or more after use. Hair testing captures the metabolites of THC deposited in the hair shaft as it grows, reflecting drug use over months rather than days or weeks.
Hair grows about half an inch per month. Standard hair testing analyzes 1.5 inches of hair from the scalp, representing roughly three months of history. Longer hair can provide a longer detection window, but most tests focus on this standard length.
This extended detection period makes hair testing suitable for employers, courts, and probation officers seeking a long-term usage profile.
How long can weed, cannabis, pot, or marijuana be detected in hair?
The terms weed, cannabis, pot, and marijuana all refer to the same substance containing THC. Therefore, the detection window in hair for each is effectively the same.
Hair testing detects THC metabolites regardless of the terminology used. Whether the sample is tested for marijuana, weed, or cannabis use, the detection period remains consistent at about 90 days or more.
How does AMH Nationwide conduct hair THC testing?
AMH Nationwide does not offer online ordering but provides a lab order and directs the requester to one of over 20,000 nationwide collection sites. Samples are collected following strict chain-of-custody protocols.
Collected hair samples are sent to one of five national lab networks: Quest Diagnostics, LabCorp, Omega Labs, United States Drug Testing Labs, and ExperTox. Each lab follows SAMHSA-aligned and CAP/CLIA-certified procedures. Every non-negative screen is reviewed by a certified Medical Review Officer to ensure accuracy and reliability.
Can one-time use or passive exposure be detected in hair?
One-time cannabis use can be detected in hair depending on the amount consumed and hair characteristics. Hair testing is sensitive to repeated or chronic use but may detect occasional use if sufficient THC metabolites are present.
Passive exposure to cannabis smoke is less likely to produce detectable levels of THC metabolites in hair. Laboratories use cut-off thresholds to differentiate environmental exposure from actual drug use.
Ready to Schedule Your Hair THC Test?
Contact AMH Nationwide to receive a lab order and find a nearby collection site. Call (877) 731-6362 to begin the testing process.
Is hair testing suitable for DOT-regulated safety-sensitive roles?
Hair testing is not approved for Department of Transportation (DOT) safety-sensitive roles. DOT regulations require urine drug testing following the federally certified urine protocol under 49 CFR Part 40.
Hair testing is used primarily for non-DOT roles or other employment situations where a longer detection window is desired. AMH Nationwide offers urine and hair testing options depending on regulatory requirements.
How much does hair THC testing cost?
Pricing for hair THC testing varies based on the testing panel selected and the detection window required. Costs can differ depending on the lab and specific services requested.
To obtain an accurate quote and discuss testing needs, contact AMH Nationwide directly. There is no online ordering; lab orders are provided by AMH, and the requester is directed to a collection site. Call (877) 731-6362 for pricing information.
Common Questions
THC can typically be detected in hair for up to 90 days or longer, depending on hair length and usage patterns.
Passive exposure is unlikely to produce a positive hair test because labs use thresholds to distinguish exposure from actual use.
No, DOT requires urine testing under 49 CFR Part 40. Hair testing is used for non-DOT roles.
A small sample of hair, usually 1.5 inches from the scalp, is collected at a certified site following chain-of-custody protocols.
Yes, every non-negative hair test is reviewed by a certified Medical Review Officer as part of standard processing.
Yes, one-time use can be detected if sufficient THC metabolites are present, but hair testing is more sensitive to repeated use.
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.