A hair follicle drug test, or a hair drug test, is done to screen a person for illicit drug use. It is also used to determine misuse of prescription medication by a person.
Drugs can be detected for as long as 90 days after their consumption in hair follicle drug tests. Because there is a difference in the rates at which the hair grows, it is difficult to tell the exact days on which the drug was consumed.
If you have used the drug for the first time, a hair follicle test may fail to detect drug use. Sometimes, these tests give a false positive result, especially in those who take prescription medications.
What drugs can typically be detected with a hair follicle test?
A hair follicle drug test is a screening test that detects past exposure to drugs and is typically used to test for drugs that include:
The test is also used to test for:
How is the hair follicle test performed?
The hair follicle test can be performed in a hospital or a lab setting. It is usually ordered as a part of the hiring process or anytime during your employment. There are at-home testing kits that are available without a prescription.
The lab technician will cut about 100 hair samples from the crown of the head. Collecting hair samples from different spots of your hair will prevent giving you a bald spot. The hair will be placed in a hair foil, which will be placed in a closed envelope.
Before the testing, the collected hair is washed and then analyzed for drugs. You do not have to wash your hair or worry about not having to dye your hair before the test.
Hair follicle testing uses two kinds of testing methods.
- Enzyme-linked immunoassay (ELISA), which gives preliminary results in 24 hours
- Gas chromatography/mass spectrometry (GC/MS), which confirms the results
You can always ask to retest if you think your test results are inaccurate.
Many insurance companies cover the expenses of the test if the test is performed in a hospital setting. If performed by your office, the expenses are paid by your employer.
Are follow-up tests necessary?
Follow-up tests may be necessary if there are concerns about the accuracy of the results. A confirmatory test may be needed if the preliminary test has come out positive.
If a drug test comes out positive, your doctor will ask you about your drug history. They will evaluate if you are an occasional drug user or need therapy for a more serious condition, drug abuse disorder.
How is a hair follicle test different from a urine drug test?
A urine drug test can only detect drugs if you have used them in the past three days. A hair follicle test can detect drugs used in the last 90 days preceding the test.
Drugs can be detected for longer in the hair and hair follicles because the drugs from the bloodstream get incorporated into the hair as it grows.
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Moeller KE, Lee KC, Kissack JC. Urine drug screening: practical guide for clinicians. Mayo Clin Proc. 2008 Jan;83(1):66-76. https://www.mayoclinicproceedings.org/article/S0025-6196(11)61120-8/fulltext
Testing.com. Hair Follicle Drug Test. https://www.testing.com/tests/hair-follicle-drug-test/
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