What are the Advantages of Hair Drug Testing?

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  • Written By: Lori Smith
  • Edited By: Michelle Arevalo
  • Last Modified Date: 09 September 2018
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Hair drug testing has increased in popularity because of its unique ability to provide a longer drug history than other methods. In fact, several months’ worth of indiscretions can be detected, as opposed to a few days or weeks from techniques that analyze the blood, urine, or saliva. Cheating on such a test is also difficult, since the hair strand samples are taken directly from the subject, usually from his or her head, making it almost impossible for someone to beat the test by passing off someone else’s specimen.

Other forms of drug testing, such as urine tests, are not always accurate because external factors may influence the results. For example, some people try to flush out their systems with rigorous exercise and drinking large amounts of water before taking the urine test. Hair drug testing is unique in that the metabolite levels are not usually affected by manipulation.

Regardless of whether drugs are smoked, snorted, or injected, the five most commonly abused classes of illegal substances — marijuana, opiates, amphetamines, phencyclidine (PCP), and cocaine — are usually detectable with hair drug testing. When the chemicals from these drugs are introduced into the bloodstream, their metabolites enter hair follicles and migrate to the hair strands. Over time, the hair grows, but the metabolites from the drug remain in place. While uncommon, it is possible to test for a drug history that dates back up to one year if the hair samples are long enough.


A laboratory technician usually collects the specimen, but just about anybody can do it as long as the hair strands are properly handled and delivered to the testing facility. In order to perform the non-invasive analysis, approximately 50 strands of hair are cut from the subject, very close to the base of the scalp. Ideally, these should be at least 1.5 in (4 cm) long in order to analyze an accurate, three-month history. In cases where an individual may be balding or have very short hair, samples can be taken from just about any place on the body.

Hair drug testing is often administered to people who are on criminal probation and required to remain drug-free in order to avoid jail. Sometimes, employers use it as a preliminary screening method, prior to hiring an applicant. Hair strand testing is generally recommended over all other screening techniques when more of an individual’s drug history is desired. Laboratory results are usually generated within a couple of days.



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