How accurate are hair follicle drug tests?

Court-ordered drug tests take place every day in Ireland for many reasons, including where decisions need to be made regarding child welfare matters or custody disputes.

Hair drug testing is one of the most effective ways to determine someone’s drug use pattern and provides a window of detection of up to 12 months.

In this article, we look at hair follicle testing in more detail, including how it works and answer the age-old question, ‘How accurate are hair follicle drug tests?’

How can drugs be detected using drug testing?

When an individual consumes drugs, they are broken down by the liver and a proportion of the drug and its metabolites are then released into the bloodstream. A small amount of the drug is then excreted by the body in a variety of ways.

In hair, a proportion of the drug finds its way to the hair follicles and becomes trapped in the medulla, which is the innermost layer of the hair. It stays there as the hair grows. Similarly, in nails, a proportion of the parent drug and its metabolites travels to the nail beds and is trapped in the keratin fibres which span the entire length of the nail.

Due to the rate of nail and hair growth, these types of tests can detect drugs for up to 12 months after consumption. For oral fluid (saliva) drug tests, the window of detection is up to 48 hours after the drug has been consumed, and for urine drug tests it is up to 4 days.

What is hair drug testing, and how does it work?

Head hair drug testing involves a cut hair sample that is analysed for the presence of drugs and their metabolites. As mentioned above, when someone consumes drugs, a small amount of the drug and its metabolites travel to the hair follicle and become trapped. After 10 days, the hair containing the drug will have grown above surface levels and after an additional two weeks it is long enough to be included in a cut sample.

There are two types of head hair drug tests that can help us to determine a pattern of drug use over a specific period. These are segmented analysis and overview analysis.

Segmented analysis, which is the most detailed type of hair strand testing, requires the head hair sample to be in 1cm sections. These samples are then analysed to provide a month-by-month profile of an individual’s drug use. This is particularly beneficial for those who need to identify drug use patterns and can be used to determine a pattern for up to 12 months.

The other type of head hair drug testing is overview analysis, which provides a more general insight into someone’s drug use. In this method, the maximum length of hair that can be tested is 3cm, which provides an overview of 3 months. These profiles can be repeated up to four times to create a 3-monthly profile for up to 12 months. Unlike segmented analysis, overview analysis doesn’t specify which month the drug was likely to be taken; only whether the drug is detected in the specific sample provided.

If head hair is not available, body hair can be used as a sample. This is collected from the underarm, face, leg, back, arm or chest. Due to the growth rate of body hair, which differs from head hair, body hair samples cannot be segmented for a month-by-month profile. They can only be used to provide a general overview of up to 12 months of drug use. Body hair is collected by weight, rather than length of hair.

How accurate is a hair follicle drug test?

Our hair drug testing is 100% accurate and reliable based on the samples we receive at our laboratory. Here are just a few more reasons why you can trust the accuracy of AlphaBiolabs’ hair strand testing for court:

  • We have over 15 years’ experience providing first-class drug testing services for the legal sector
  • We have invested in the very latest drug testing technology for our state-of-the-art toxicology laboratory
  • We employ some of the foremost scientists in Europe
  • We follow cut-off guidelines for hair drug testing, as set by the Society of Hair Testing (SoHT)
  • Our laboratory is accredited by UKAS to the quality technical standard of ISO 17025 (No. 2773) and certified to ISO 9001
  • All our legal sample collections are carried out by professional sample collectors, under strict chain of custody conditions
  • Our toxicologists work within the framework of Family Law and follow Part 25 of the Family Procedure Rules (2010)

What factors can affect the accuracy of hair drug testing?

It is widely known that certain hair treatments such as perming, straightening, bleaching, and dyeing can potentially impact hair strand test accuracy. This is because the chemicals used in these types of hair treatments can damage the hair shaft and alter the concentration of the drug.

For this reason, reputable testing laboratories like AlphaBiolabs always require a full disclosure of any recent hair treatments, so that this can be taken into consideration when preparing hair drug testing results. We will also record details of any medical conditions as well as any medications taken.

Trained sample collectors at AlphaBiolabs are also fully aware of the ways that individuals may try to ‘cheat’ hair drug tests, including trying to use a pre-cut sample that isn’t theirs or wearing a wig, and can therefore mitigate any attempts to ‘cheat’ the test.

Drugs can potentially be transferred to the outside of the hair through smoke or via direct contact. Therefore, when the hair samples arrive at our laboratory, they are always chemically washed three times to remove any surface layer drugs. This washing solution is then kept for further analysis, if required.

Where can I get a hair drug test?

AlphaBiolabs has extensive experience providing drug testing services for local authorities, family law professionals and social workers. We have invested in the very latest technology for our state-of-the-art toxicology laboratory, employing the very best scientists, so you can be confident of receiving a 100% accurate result.

We have a nationwide network of professional sample collectors, and all sample collections are performed under strict chain of custody conditions.

We also offer free sample collection for legally-instructed hair drug tests from our Dublin walk-in centre.

For expert advice on hair drug testing, or to request a quote, call AlphaBiolabs’ Legal team on 0140 29466 or email

Alternatively, complete our online quote form, and a member of the team will be in touch to discuss your needs.

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Gail Evans AlphaBiolabs

Gail Evans

Technical Trainer at AlphaBiolabs

A professionally-trained forensic scientist, Gail joined AlphaBiolabs in 2012 and holds the role of Technical Trainer.

Her day-to-day responsibilities include delivering in-depth training sessions both internally and externally, covering DNA, drug, and alcohol testing.

Throughout her career at AlphaBiolabs, Gail has held a variety of roles, including within the Legal and Workplace sectors of the business.

Before joining the company, Gail was a practicing forensic scientist with 25 years’ experience working for the Forensic Science Service, attending scenes of crime, and analysing physical and biological material with potential evidential value.

Gail also holds qualifications in chemistry and is a Lead Auditor for the ISO 9001 standard, the international standard for quality management.

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