Hair Follicle Drug Testing

Hair Follicle Drug Testing

Recently, we have been seeing more interest in hair follicle drug tests from lawyers, employers, and medical professionals alike. These tests are able to determine whether or not a person has been taking illicit drugs or abusing their prescription medication.

We will be discussing how a hair follicle drug test works, how to use an at-home testing kit, and what the results of a test mean. We’ll also look at the costs of these tests, how accurate they are, if people without hair are able to provide samples, and how hair follicle tests stack up to traditional urine drug testing.

What Is a Hair Follicle Drug Test?

Hair follicle drug tests are used to determine if someone has been misusing prescription medication or taking illicit drugs across a period of time – typically three months for hair samples taken from the head.

Testers are able to check for specific drugs with hair follicles, or they could run even a single hair through several different tests for drugs and drug classes.

How Far Back Can Hair Follicle Tests Detect Drug Use?

While urine tests typically only detect drug use within the past few days, hair follicle tests can unveil a much longer history. In general, a standard 1.5 inch hair sample taken close to the scalp can provide a window into the last 90 days of drug use.

However, some labs offer hair follicle tests that can look even further back, up to a year or more, by testing longer hair samples. The hair sample is cut into segments, with each segment representing about 30-90 days. This allows the test to provide a detailed timeline of an individual’s drug use over an extended period.

It’s important to note that it takes approximately 5-7 days for drugs to become detectable in hair after use. So very recent drug use may not show up on a hair test.

Why Is Hair Follicle Testing Necessary?

There are several reasons one must be tested for drugs, including employment, medical, and legal purposes.

Some companies will require their potential employees to pass a drug test during the application process, especially with jobs that have a high degree of risk. Employers will also sometimes conduct random drug tests on their current employees, or someone may be required to go through drug testing after a serious accident or incident.

In the UK, the law is clear on drug testing and the legal requirements of employers. The laws surrounding drug testing can vary from state to state in the United States. Certain states prohibit random drug testing of employees. For these states, employers are required to provide evidence that they are justified in requesting a drugs test for a specific employee.

The courts might require drug testing for people who are at risk of abusing drugs and alcohol. Healthcare providers may also require people who are at risk of abuse to undergo drug testing. Please note that drug tests will generally require written consent from the person being tested.

What Happens During a Drug Test?

Hair follicle tests are performed at home, at the workplace, or in a healthcare setting. For the actual test itself, a small hair sample is taken from a person’s scalp and then sent to a laboratory where it is tested overnight.

Some foods – such as poppy seeds – and prescription medications could cause a false positive result. Hair samples are put through a two-step process to verify the authenticity of results. The first of these steps is using an enzyme-linked immunosorbent assay (ELISA) test. The ELISA test is a rapid screening method.

Should there be a positive result from the ELISA test, then a technician runs the sample through confirmatory chromatographic testing – such as gas chromatography-mass spectrum (GC-MS) in order to rule out a false positive.

How to Do an At-Home Test

Online providers offer at-home testing kits for those who want them. These kits come with a pre-paid envelope to mail the hair sample to a laboratory and instructions on conducting the test.

How to perform a hair follicle test at home:

  1. Read through the instruction manual included with the kit
  2. Collect a hair sample according to directions
  3. Wrap the sample in foil
  4. Place the hair sample in the envelope provided
  5. Mail the sample to the laboratory for analysis

People can typically access the results of the test by calling a freephone number or by going online and signing in with the unique identification number on their kit.

What Do the Results of a Test Mean?

Hair follicle drug tests can come back with a positive, negative, or inconclusive result.

  • Positive

A hair sample that produces a positive result with ELISA testing is sent through a second test, such as a GC-MS test. If the confirmatory testing also comes back positive, then this means the laboratory confirmed that there were drug metabolites in the hair sample.

  • Negative

Negative results for hair follicle tests mean that the laboratory was unable to detect any drug metabolites in the hair sample. It may also mean that the ELISA test came back positive but GC-MS testing was unable to confirm the result.

  • Inconclusive

If something goes wrong or a sample is contaminated somehow, it may produce an inconclusive test result. The person may be required to provide a new hair sample for testing if the results are inconclusive.

Can You Beat a Hair Follicle Drug Test?

Many people wonder if it’s possible to cheat a hair follicle drug test. While some claim that certain shampoos, cleansers or home remedies can help you pass, the reality is that none of these methods are foolproof.

The drug metabolites are embedded inside the hair shaft, so external washing or treatments won’t significantly alter the test results. Even bleaching or dyeing your hair is unlikely to make a major difference, although it could potentially reduce the drug concentrations somewhat.

The most effective way to pass a hair drug test is simply to abstain from drug use for a sufficient period of time before the test. For those who can’t do that, the only other surefire method is to shave all the hair off your body – but that’s likely to raise suspicions on its own!

So in most cases, trying to cheat the test is very risky. Your best bet is to be honest with the tester about any substances you’ve used.

Accuracy of Hair Follicle Drug Tests

Hair follicle drug tests are performed to determine whether someone has used certain substances at any point in the past three months. However, such tests are unable to pinpoint the exact time that drugs were used because different people have different rates of hair growth.

While hair samples are subjected to a two-step testing process, they can’t be considered completely 100% accurate.

There are several factors that affect the drug metabolite levels in hair, including:

  • The structure of the drug compounds
  • The quality of the drugs consumed
  • How much the subject sweats
  • How much melanin (dark hair pigment) there is in the subject’s hair – some drugs bond better to melanin
  • Bleaching and colouring hair

It’s worth noting that standard hair products such as shampoos and styling products shouldn’t affect test results.


Hair follicle home testing kits are available at a range of prices. They can be purchased directly through a manufacturer’s website, or can be purchased through pharmacies and other online methods.

There are some drug testing kits that can be purchased at a flat fee, including the cost of shipping and laboratory testing. Other kits see the person pay the basic cost of the kit and then extra money based on the drugs being tested for.

Employers that want to drug test employees must cover any costs associated with taking the test, taking into account the time of the person being tested.

Health insurance companies may cover the cost of a hair follicle drug test done for medical purposes.

What if Someone Doesn’t Have Hair on Their Head?

A person not having hair on their head doesn’t mean they can’t be tested. The hair samples can be taken from armpits or from facial hair. However, the hair that is used for the test must be at least 0.5 – 1.5 inches in length. If the subject has shorter hair then testing may need to wait until it has grown.

People who have no hair at all on their bodies may not be able to provide hair for a follicle test.

Hair Follicle Drug Tests vs Urine Drug Tests

Hair follicle tests can offer a wider window of detection compared to urine tests.

Urine drug tests come with a detection window of between 10 hours and 1 week for most drugs other than cannabis, which can remain present in urine for up to a full 30 days.

On the other hand, hair follicle tests can test for drug use up to three months before testing with hairs taken from the scalp.

Urine tests are able to detect more recent drug use, with hair follicle tests helping to identify long-term regular drug use.

Tampering with a urine sample is also easier than tampering with a hair sample, which could give follicle tests the advantage over urine tests when the test is performed in a laboratory setting.

While drug screening tests generally still use urine samples, hair follicle samples can be used to find people taking drugs regularly across the long-term.

Photo: “Hair Follicle Drug Testing” by Anthony Cunningham for Zoom Testing

Zoom Testing is a leading UK drug testing company and a supplier of Drug Test Kits.

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