What to Know About a Hair Follicle Drug Test

A hair follicle drug test is one way to screen for recreational drug use or prescription drug abuse. A section of hair, about 200 strands, is sent to a lab for testing. The test can pick up drugs or drug metabolites inside the hair shaft that have been deposited there through the bloodstream.

Like urine tests, the drugs that can be detected will vary depending on the panel that is chosen. A standard five-panel test looks for:

Read on for more information about hair follicle drug testing, how it’s done, and how accurate it is.

Forensic Science in Lab

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Why Is a Hair Follicle Drug Test Necessary?


Drug tests are used to show drug use or misuse. One of the benefits of follicle drug tests is that they can show whether someone used or abused drugs as far back as three months prior to the test. Follicle drug tests can be used in:

  • Workplaces to screen applicants, periodically test employees, or to test employees after an accident or other issue
  • Forensic and legal testing, including during criminal investigations or child protection cases
  • Drug rehabilitation programs, to check for long-term drug use/abuse

How a Hair Follicle Drug Test Works

When a person uses drugs, they go into the bloodstream. Because each hair follicle has a blood vessel, drugs are able to travel through the bloodstream into the hair follicle.

To do a hair follicle drug test, a sample of hair is taken from the person’s head, close to the scalp. The sample needs to be 1.5 inches long and about as thick as a pencil. It is then sent to a lab for analysis.

The test can detect metabolites of drugs, which are substances made from the breakdown of drugs. It has the ability to detect drugs used within the past 90 days.

Home Hair Tests

At-home hair drug tests are available in stores and without a prescription. They involve collecting hair and then sending it to a lab for analysis.

How to Use a Home Hair Test

Using a home hair test is fairly easy. First read the instruction manual so you know what to do. Take the hair sample necessary based on the directions and wrap it in the foil provided. Then put the foil-wrapped hair in the container or envelope that came with the kit, and mail it to the laboratory. It will then be analyzed.

You can typically get the results by calling the phone number provided or going online and using the specific ID number that came with your kit.

Is a Home Hair Follicle Test Accurate?

Because home tests are sent to a lab, they're comparable to regular hair follicle drug tests. Neither type of test is 100% accurate, even though they go through a two-step process.

Understanding Hair Follicle Test Results

The results of the test will be reported as positive, negative, or inconclusive. Here's what those terms mean.

Negative

A negative result means that no drugs or drug metabolites were found in the sample. It doesn’t mean the person hasn’t used any drugs, however. The person could have used a drug very recently, before it had the chance to show up in the hair, or they might not have used enough of the drug to be detected. They could also have used other drugs that the test didn't screen for.

Positive

A positive result means that the drug or drug metabolite was found in the hair sample. There are not standard positive cutoff values for all laboratories yet, so this may vary among labs.

Inconclusive

An inconclusive result may mean the hair sample was contaminated or something went wrong with testing. You might be asked to provide another sample.

How Accurate Is a Hair Follicle Drug Test?

Hair follicle drug tests are very accurate in detecting long-term drug use, because of the large window of time they can detect. However, the test may not be able to detect if someone uses drugs very infrequently or used drugs shortly before the test. It takes about seven to 10 days for drug use to show up in the hair. Hair needs time to grow, and so the drug may not be in the hair follicle.

There are other factors that may lead to inaccurate or biased results, including:

  • Contaminated hair: Even if you don't use a drug like cocaine, being around it can cause cocaine molecules to bind to your hair. It may not be fully removed with washing, leading to a false positive.
  • Hair color: Some drug metabolites bind more easily to melanin in darker hair than lighter hair, which can lead to falsely high concentrations.
  • Hair treatments: Shampooing, coloring, relaxing, and bleaching the hair can impact the metabolite concentration that is detected; in these cases, untreated hair from the body might be a better choice for testing.

Can a Hair Follicle Drug Test Identify Date of Drug Use?

No, it cannot identify the specific date of drug use. It can only show whether a substance has been used within the past 90 days.

How Much Does a Hair Follicle Drug Test Cost?

The cost of a hair follicle drug test can vary, depending on the kind of hair follicle test ordered (the number of drugs in a screen can differ), where you go for testing, and who ordered the test.

Your health insurance plan may cover the costs, or your employer may, if they are ordering it. If you are buying a home test, you pay for all of the associated fees. Many at-home tests will charge an extra fee for the laboratory analysis, adding to the total cost of the test.

Hair Follicle Drug Test vs. Urine Drug Test

A urine drug test can only detect drug use going back several days, while a hair follicle drug test can pick up on drug use going as far back as 90 days. Some urine tests provide instant results, but hair tests must be sent off to a lab for completion.

Research has shown that urine testing is better able to pick up self-reported use of cannabis, heroin/opioids, benzodiazepines, and methadone, but hair drug tests are better able to pick up cocaine. For unreported use, urine testing was more effective at picking up cannabis and benzodiazepines, and hair testing was better able to detect cocaine and oxycodone.

What If I Have No Hair?

If someone has no hair on their head, a body hair sample can be collected. It should be noted, though, that body hair tests can detect drugs used over a longer period of time because the hair grows more slowly. Scalp hair generally has a detection window of about three months.

Summary

While most people may be familiar with urine screening drug tests, hair follicle drug tests are also used, although not as widely. Whereas urine drug tests can detect recent drug use, hair follicle drug tests have a much larger window of detection—about 90 days. This can be especially helpful if you’re looking for something like prescription drug misuse.

A Word From Verywell

Although hair follicle drug tests can be effective, they are not 100% accurate. It’s important to know that false positives can occur, and that they're more common in people with darker hair.

Frequently Asked Questions

  • How long can drugs be detected in a hair follicle test?

    Drugs can be detected in a hair follicle test for about 90 days. However, if drugs were used for the first time within seven to 10 days of the test, they may not show up, because it takes time for the hair that contains the metabolites to grow.

  • Can a hair follicle test detect one-time use?

    It may or may not, especially if the drug was used within seven to 10 days of the test. The test is not 100% accurate.

  • What can cause a false positive hair follicle test?

    Certain foods and medications can cause false positives. Cold remedies, decongestants, or hay fever medicines can show up as amphetamines, and poppy seeds may show up as opiates.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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