A hair strand drug test examines clipped hair to check for illegal drug use and misuse of prescribed medicines. Although often called a “hair follicle test,” the analysis inspects only cut hair strands, not the follicles beneath the scalp.
During this procedure, a small bundle of hair is cut from your head with scissors. The sample is analyzed for evidence of drug exposure during the roughly 90 days prior to collection. It’s commonly used to screen for:
- amphetamine
- methamphetamine
- ecstasy
- cannabis
- cocaine
- PCP
- opioids (codeine, morphine, 6-acetylmorphine)
Whereas a urine drug screen can detect drug use over the previous few days, a hair drug test can reveal drug use across the past 90 days. Employers often request hair testing as part of pre-employment screening or for random workplace testing.
What happens during the test?
A hair strand test can be performed in a laboratory or medical setting, or using a mail-in kit provided by your workplace. You can also buy at-home hair test kits online.
If your employer mandates the test, you may be required to be supervised while the sample is collected.
You may wash, color, or style your hair before the test without altering the results.
After verifying identity details, the collector will cut about 100 to 120 hairs from the crown area of your head. To avoid a noticeable thin spot, hair may be taken from several nearby locations on the crown.
If there is insufficient scalp hair, the collector may take body hair instead. The hair sample is wrapped in foil and sent in a secure envelope for expedited laboratory analysis.
Understanding your results
A negative finding can be reported within 24 hours after the sample is taken. The initial screening method, called ELISA, is used to determine whether the hair sample shows no evidence of drug use.
A negative result suggests no illicit drug use in the preceding 90 days. Any nonnegative outcome requires follow-up testing for confirmation.
A positive result is typically confirmed within 72 hours. All nonnegative screens are retested using gas chromatography/mass spectrometry (GC/MS). This confirmatory test verifies a positive finding and identifies the specific substances present.
An inconclusive outcome is uncommon when collection and handling are done correctly. Occasionally, improper collection may lead to specimen rejection, in which case the test might be repeated.
The laboratory performing the analysis will send results to the ordering individual or organization using confidential channels, such as a secure online portal or phone call.
Because laboratory results are protected health information, you must sign a release before results are shared with your employer.
Can the test identify the date of drug use?
A hair drug test provides an overview of repeated drug exposure over approximately the last 90 days. Because hair growth rates differ among individuals, the test cannot precisely pinpoint the exact dates drugs were used within that window.
How accurate is the test?
Hair samples are collected and processed following strict protocols to maximize accuracy. During analysis, the hair is washed and evaluated for environmental contamination that could affect results.
Washing, coloring, or styling hair does not change the test outcome.
Laboratories use two tiers of testing to reduce the chance of false positives. The initial ELISA screen can yield a negative or presumptive positive within 24 hours.
The confirmatory GC/MS test is widely accepted and can detect specific substances—one study indicates it can identify as many as 17 different drugs. GC/MS also helps prevent false positives caused by foods such as poppy seeds or hemp seeds.
Research shows hair testing covers a longer time span than urine testing, though urine tests can be more sensitive for recent use.
Certain prescribed medications can affect results. If you take an opioid pain medication as prescribed, it will appear on the test; in such cases employers typically request prescription documentation.
If you believe your results are erroneous, you may request a retest through your employer promptly.
How much does the test cost?
Hair drug testing generally costs more than urine testing, though prices vary by test type. Reported prices for at-home kits range from about $65 to $150, while tests done in hospitals or labs can run between $100 and $200.
If you’re an employee required to undergo a workplace hair strand test, your employer is legally required to compensate you for time spent and to cover the cost of the test.
If the drug screen is part of pre-employment checks, the employer is not obliged to pay you for your time.
Many insurers will cover drug testing when it’s performed for medical reasons in a hospital setting, such as during an inpatient stay or in the emergency department.
Hair vs. urine drug test
The primary difference between hair and urine drug tests is the length of the detection window.
Urine tests typically detect drug use within the previous few days. Hair tests are unique in their ability to detect repeated drug use going back up to 90 days.
This is because drugs in the bloodstream can become incorporated into hair cells as hair grows. The sweat and sebum on your scalp may also contribute to drug residues in existing hair strands.
Due to hair growth timing, drugs are generally not detectable in hair until about five to seven days after use. Therefore, hair testing is not suitable for identifying very recent drug use, such as in the case of an on-the-job incident.
If you have concerns about your test outcomes, reach out to the medical review officer (MRO). An MRO reviews drug test results and can help interpret them.
The takeaway
Hair drug tests can reveal drug use going back as far as 90 days because drug compounds present in the bloodstream are incorporated into hair cells during growth.
These tests are not ideal for detecting very recent drug use, since it can take five to seven days for substances to be detectable in hair. Urine tests are better suited for identifying recent use.
If you’re on prescribed medicine, inform the test administrator—prescriptions can produce positive results and documentation may be required.
For related topics, you may find information on hair miniaturization and how long does weed stay in your system helpful.
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