How A Hair Follicle Drug Test Works | Detection Times & What To Expect

Saliva tests, blood tests, urine tests, and hair follicle drug testing can all be used to detect the use of certain controlled substances with high accuracy. 

However, each option comes with its own advantages and limitations that lab professionals, employers, and other authorities should consider.

Drug Detection Times For Hair Follicle Tests

Hair follicle drug tests can, generally, detect illicit drug use that occurred in the past 90 days. However, depending on individual hair growth rates, hair follicle tests cannot detect drug use that occurred five to seven days before the hair sample was collected.

Urine drug testing, which has a detection window of 3-5 days at most, is recommended for identifying recent drug abuse.

How Hair Tests Work

Hair follicle drug testing can be used to screen for illicit drug use, and can also detect legal prescription medication use.

As strands of hair grow from hair follicles, they trap small amounts of the substances present in the body at the time. This means that those who use drugs of abuse will tend to have tiny traces of these drugs, or their metabolites, present in the hair shaft for a lengthy period of time.

Testing Process

During the collection process, around 120 head hairs will likely be cut, placed in foil, and sealed. This sample of hair will be around the thickness of a straw and can be taken from different locations all around the head.

In special cases, like when a person has little or no hair on their head, body hair from the armpit or some other location can be substituted instead.

This hair sample is then sealed in foil, placed in a secure package overnight, and mailed to a hair analysis laboratory where it is washed, prepared, and evaluated in either one or two testing stages:

• ELISA, or enzyme-linked immunosorbent assay, is a test used to broadly identify the absence or presence of illicit drug use
• gas chromatography/mass spectrometry (GC/MS) is used to confirm a positive ELISA result to identify the specific drugs a person has taken

Once the lab has the results, they will forward them to the individual or organization that ordered the test using a secure form of communication.

Possible Hair Drug Testing Results

There are three possible results for a hair follicle drug test:

• negative result: an ELISA screening, performed within 24 hours of hair removal, did not detect the use of any illicit drug use, or a false-positive was identified through GC/MS testing
• positive result: the ELISA screening detected drug use and follow-up GC/MS testing confirmed this result, identifying the type of substance that was abused
• inconclusive result: problems with the test procedure, hair specimen, or specimen collection have invalidated the test results and the tests should be repeated

Limitations Of Hair Follicle Tests

While laboratory hair follicle tests are reliable, even if the hair was bleached or heavily treated, there are certain limitations to this testing option that should be noted.

Types Of Drugs Hair Follicle Tests Can Detect

It is impractical to test for each and every controlled substance during routine drug screenings. Because of this, broad categories of drugs are screened for instead, specifically:

• amphetamines
• cannabis
• cocaine
• ecstasy
• methamphetamine
• PCP
• opioids/opiates
• benzodiazepines

GC/MS testing may or may not be able to identify the specific drug present in the sample, depending on the situation. It can also help identify common false positives like poppy seeds and opium, and ADHD meds and methamphetamine.

Legal Concerns

Because lab results are considered confidential health information, participants must sign a release before their results can be passed along to the organization that ordered the test.

In addition, workplace drug testing ordered for current employees must, by law, be paid for by the employer, who must also pay the employee for their time.

Home Test Kits

DIY/home hair follicle test kits, which are available online, tend to be less precise than professional tests and do not include GC/MS testing, which can only be performed inside a specialized laboratory.

Dosage/Frequency Of Use

Drug metabolites must accumulate in the hair to a certain level in order to be detectable. This means that hair follicle testing is most reliable when a drug is in a frequent and/or heavy pattern.

Infrequent drug use may not trigger a positive result, depending on the testing method, substance, dosage, and an individual’s metabolism.

If you are concerned that your drug test results may cause you trouble at work or in the legal system, please consider reaching out to Ark Behavioral Health today for professional addiction treatment services.