Understanding If a Hair Follicle Test Can Detect Drug Use Up to 9 Months

Can a hair follicle test go back 9 months?

A hair follicle test typically detects drug use within the last 90 days, which corresponds to approximately 1.5 inches of hair growth. Since hair grows on average about half an inch per month, testing a standard 1.5-inch hair sample covers roughly three months of drug history.

Testing hair samples beyond 3 months, such as 9 months, is not standard practice because hair samples longer than 1.5 inches are less reliable for accurate segmental analysis. Laboratories generally do not test hair segments corresponding to 9 months due to variability in hair growth rates and potential external contamination.

Therefore, a hair follicle test cannot reliably go back 9 months to detect drug use. For longer detection windows, other testing methods or repeated testing over time may be necessary.

How do AMH Nationwide labs process hair follicle drug tests?

AMH Nationwide routes hair follicle tests through five national lab networks: Quest Diagnostics, LabCorp, Omega Labs, United States Drug Testing Labs, and ExperTox. Each lab follows strict chain-of-custody and testing protocols.

Hair samples are collected at a designated site and sent to the lab, where they undergo immunoassay screening. Any non-negative results are confirmed and reviewed by a certified Medical Review Officer (MRO) to ensure accuracy and interpret findings within clinical context.

This process guarantees reliable results for workplace, court, or personal drug testing purposes.

What substances can a hair follicle test detect and for how long?

Hair follicle tests commonly detect drugs including cocaine, marijuana (THC), opiates, amphetamines, methamphetamine, phencyclidine (PCP), and others. The detection window is generally up to 90 days.

Because substances are deposited in hair follicles from bloodstream circulation, the test reflects drug use during hair growth. Hair color, cosmetic treatments, and hair type can influence detection sensitivity but do not extend the detection window beyond approximately 3 months.

Is hair follicle testing accepted for DOT-regulated safety-sensitive positions?

No. DOT-regulated drug testing requires urine testing under the federally certified urine protocol defined by 49 CFR Part 40. Hair follicle testing is not approved for DOT safety-sensitive roles.

Hair testing is used for non-DOT roles when employers or individuals want a longer detection window than urine testing provides.

Can passive exposure or hair treatments affect hair follicle test results?

Passive exposure to drugs is unlikely to produce a positive hair follicle test because drugs are incorporated into hair from the bloodstream rather than external contamination.

Chemical treatments like bleaching, dyeing, or perming can reduce drug concentrations in hair and potentially cause false negatives, but they do not extend detection windows.

Laboratories follow procedures to detect and account for such factors during analysis.

How do I arrange for a hair follicle drug test through AMH Nationwide?

AMH Nationwide provides the lab order and directs you to one of over 20,000 collection sites nationwide. There is no online ordering available.

To schedule a hair follicle test, call (877) 731-6362. Pricing varies depending on the test panel and detection window requested.

All test results are reviewed by a certified Medical Review Officer as part of standard processing.

Common Questions