How long can hair drug test go back
How Long Can Hair Drug Test Go Back to Detect Drug Use History
How long can hair drug test go back depends on the length of hair sampled, typically up to 90 days or 3 months. Hair follicle drug tests detect drug metabolites embedded in hair shafts, providing a longer detection window than urine or saliva tests. Call (877) 731-6362 to schedule testing at nationwide collection sites.
How long can hair testing for drugs go back?
Hair testing for drugs can typically go back about 90 days or 3 months, depending on the length of hair collected. Hair grows approximately half an inch per month, and standard testing uses 1.5 inches of hair closest to the scalp to detect drug use during that period.
Longer hair samples can extend the detection window proportionally, but most labs limit samples to 1.5 inches due to standard protocols and accuracy considerations.
How does a hair follicle drug test detect drug use over time?
A hair follicle drug test detects drug metabolites that enter the hair shaft from the bloodstream after drug use. As hair grows, these metabolites become trapped in the hair cortex, preserving a timeline of drug exposure.
Because hair grows slowly, the test can show drug use history over months, unlike urine or saliva tests that detect only recent use. The tested hair sample is collected at a designated collection site and sent to one of five national lab networks: Quest Diagnostics, LabCorp, Omega Labs, United States Drug Testing Labs, and ExperTox.
How long do drugs stay in your hair and which drugs can be detected?
Drugs stay in hair follicles as long as the hair remains on the scalp, typically up to 90 days of growth. Common drugs detected include marijuana, cocaine, opiates, amphetamines, methamphetamines, PCP, and synthetic opioids.
Hair tests detect metabolites, not the parent drug, which confirms actual drug use rather than environmental exposure.
Can hair drug tests detect one-time or passive drug exposure?
Hair drug tests detect drug metabolites from actual ingestion, so one-time use may be detectable depending on timing and hair length. Passive exposure, such as environmental smoke, typically does not produce positive results because metabolites must enter the bloodstream to be incorporated into hair.
Certified Medical Review Officers review every non-negative screen to ensure accurate interpretation.
Schedule Your Hair Drug Test Today
Call (877) 731-6362 to get lab orders and find a nearby collection site for hair follicle drug testing with comprehensive detection up to 90 days.
How long can hair follicle drug test go back for DOT-regulated testing?
The Department of Transportation (DOT) requires urine drug testing under federally certified protocols (49 CFR Part 40) for safety-sensitive roles. Hair testing is not accepted for DOT-mandated tests but is used for non-DOT employment or legal testing.
For non-DOT roles, hair testing offers a longer detection window, typically up to 90 days.
How do I arrange a hair follicle drug test with AMH Nationwide?
AMH Nationwide provides lab orders and directs the requester to one of 20,000+ nationwide collection sites. There is no online ordering. To arrange testing, call (877) 731-6362. The hair sample is collected by trained personnel and sent to one of five national labs for analysis.
Results are reviewed by certified Medical Review Officers before reporting.
Common Questions
Hair follicle drug tests generally detect drug use for up to 90 days or 3 months, based on hair length and growth rate.
Yes, depending on the timing and hair sample length, a one-time drug use can be detected as metabolites incorporate into hair after ingestion.
No, passive exposure usually does not produce positive results because drug metabolites must enter the bloodstream to be incorporated into hair.
No, DOT regulations require urine testing under federal protocols. Hair tests are used for non-DOT testing.
A small hair sample, typically 1.5 inches long, is cut close to the scalp by trained collectors at authorized collection sites.
All non-negative hair drug test results are reviewed by certified Medical Review Officers to ensure accuracy before reporting.
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.