Test Quick Guide

Hair follicle drug testing detects evidence of drug use or misuse in a sample of hair. Drug testing can screen for the use of illegal drugs, as well as the misuse of prescription medications, over-the-counter medicines, and legal substances including alcohol and tobacco.

During hair follicle drug testing, scissors are used to remove a small sample of hair. Compared to other forms of drug testing, hair follicle drug testing offers advantages such as a long detection window and the ability to estimate patterns of drug use over time.

About the Test

Purpose of the test

The purpose of a hair follicle drug test is to detect evidence of drug use or misuse in a sample of a person’s hair. Drug use refers to the use of illegal substances. Drug misuse describes using prescription drugs in a manner that isn’t prescribed by a doctor or using legal substances in an unhealthy way.

Hair follicle drug testing may be used over other types of drug tests because of its ability to show a longer history of drug exposure. This type of test may be helpful when testing for chronic drug use or misuse, understanding long-term patterns of use, and confirming periods of abstinence. Hair follicle drug testing may be used in several ways:

  • Employment testing: Employers may require drug testing in many situations, including when screening job applicants, for periodic or random detection of drug use by employees, or after a workplace accident. Although urine drug tests are the most common method of detecting drug use in workplaces, hair follicle drug testing may be used by some employers.
  • Forensic and legal testing: Hair samples may be collected during criminal investigations to evaluate for drug use or misuse in drug-facilitated crimes and child protection cases.
  • Medical testing: Although doctors rarely analyze a hair sample to evaluate a person’s health, there are situations in which a hair test can provide doctors with helpful information. For example, hair testing can assist in post-mortem evaluations of long-term drug use or misuse.
  • Drug rehabilitation programs: Hair testing may be used in addiction medicine to detect chronic drug use and misuse, as well as understand periods of abstinence.

What does the test measure?

Hair follicle drug tests identify drugs or drug metabolites in a sample of hair. A drug metabolite is a substance that is generated in the body as a drug is being broken down and eliminated.

Once a drug is consumed, it enters the bloodstream and travels throughout the body. As the drug is broken down in the body, drugs and drug metabolites enter the core of the hair through the hair follicle, sweat glands, and oil glands on the scalp. Drugs and drug metabolites remain in the hair as it grows, which occurs at a rate of about one-half inch each month. Some drug metabolites attach to melanin, the part of a hair follicle that gives hair its color.

Hair follicle drug testing has a longer window of detection than other types of drug tests. While drug use and misuse may not appear in the hair until 7 to 10 days after drug exposure, once it enters the hair it remains for weeks, months, or even years. While testing hair can provide information about patterns of drug exposure, hair follicle drug testing cannot detect current intoxication.

How long drugs remain detectable in hair is called the window of detection. The length of the detection window varies based on a number of factors, including the amount and frequency of drug use or misuse and the rate at which the drug is metabolized in the body. Some drugs continue to enter new hair growth for months after a person’s last drug exposure.

The window of detection also varies based on the amount of hair tested. Although longer samples of hair can be tested for drug exposure over a longer period of time, a standard sample of hair from the scalp is 1.5 inches and provides information about approximately 90 days of past drug exposure. A hair sample taken from a different part of the body where hair grows more slowly may have a detection window of up to 12 months.

Drugs that can be detected during hair follicle drug testing include:

A hair follicle drug test may focus on detecting one specific drug in the hair or on detecting several substances in a hair follicle drug panel. One commonly used hair follicle drug panel looks for evidence of the use of five drugs or drug classes: marijuana, amphetamines, cocaine, PCP, and opioids.

When should I get a hair follicle drug test?

Hair follicle drug testing is used in workplace testing, legal and forensic testing, medical testing, and for measuring the patterns of illegal and prescription drug use.

The use of drug tests is impacted by federal, state, and local laws. Professional organizations advocate for the ethical use of drug testing, often emphasizing the importance of patient education and consent before conducting a drug test.

Many parents consider using drug testing as a tool to prevent or confirm the use or misuse of drugs in children and adolescents. The American Academy of Pediatrics advises against this practice, citing the lack of evidence that drug testing reduces drug use in children and adolescents, the potential for misinterpreting test results, and the negative impact on the relationships between parents and children caused by testing.

Finding a Hair Follicle Drug Test

How to get tested

A sample of hair can be collected at home, at a laboratory, or in a medical setting.

Hair follicle drug testing can be ordered by a doctor or an administrator of a program that requires drug testing. Hair follicle drug tests can also be purchased through retailers without a prescription.

Can I take the test at home?

At-home collection kits allow users to collect hair samples and mail them to a laboratory for analysis. At-home hair follicle drug test kits are available for purchase online and over-the-counter at a variety of retailers. Some at-home hair follicle drug tests look for only one type of drug while others offer test panels that look for several drugs at once.

When considering the use of an at-home hair follicle drug test, it’s important to consider whether the company offers confirmatory testing for positive screening results.

How much does the test cost?

The cost of hair follicle drug testing depends on where a sample is collected, the type of hair follicle drug test ordered, and who is paying for testing. Patient costs may be covered by an individual’s health insurance or the organization requiring a drug test. In other cases, patients may choose to pay out-of-pocket for laboratory-based or at-home collection kits.

Patients’ costs vary considerably, so it’s important to discuss questions about the cost of testing with the doctor, insurance provider, or organization ordering the testing.

Taking a Hair Follicle Drug Test

Hair follicle drug tests are performed on a sample of hair, usually collected from a person’s scalp. Once collected, hair samples are sent to a laboratory for testing.

In some cases, the collection of a hair sample will be performed by a trained professional to prevent tampering, contamination, or substitution of the sample. Before taking a hair follicle drug test, patients should ask the organization requiring drug testing about requirements for hair sample collection.

Before the test

Although there are no special precautions necessary before a hair follicle drug test, patients should inform their doctor of medications or supplements that have recently been taken. Patients should also inform their doctor of any recent hair treatments, including shampooing, as these may affect test results.

During the test

Collecting a sample of hair at a laboratory or at home involves cutting a lock of hair about the thickness of a pencil from the back of the head using scissors. During the collection process, the person cutting the hair should wear gloves to avoid contamination of the hair sample.

Hair is collected as close to the scalp as possible, near the hair’s root, to provide information about recent drug use. A standard sample of hair is around 1.5 inches, although in some cases a longer sample may be collected for additional history of drug use and misuse.

If patients don’t have sufficient hair on their scalp, hair may be collected from the face, armpit, pubic area, or another unshaven part of the body. Collecting hair is not associated with any risks, although some patients may experience embarrassment or anxiety during sample collection.

After the test

After a hair sample is collected, it is packaged according to instructions contained in the collection kit and sent to a laboratory for testing. There are no restrictions on activity after a hair follicle drug test.

Once received by the laboratory, the hair sample may be washed prior to testing. Specialized methods of washing the hair sample remove some external contaminants, dirt, and grease from the surface of the hair. Drugs inside the hair are unaffected by washing.

Hair Follicle Drug Test Results

Receiving test results

Results of hair follicle drug testing are generally available within a few business days after the laboratory receives the sample. Processing times vary, so patients may find it helpful to ask their doctor or the laboratory when to expect results.

Depending on the reason for testing, patients may learn about their test results through a health care professional or the organization that required testing.

Interpreting test results

The results of hair follicle drug tests may be reported as positive or negative. Positive test results indicate that a drug or its metabolite was detected in the sample of hair submitted for testing.

Negative test results indicate that no drugs or drug metabolites were detected in the hair sample. Negative results suggest that a person didn’t consume the drug targeted by the test, that they used a drug outside of the test’s detection window, or that an insufficient amount of the drug was consumed to be detected in the hair.

When interpreting results, it may be helpful to understand the laboratory method used for testing. Laboratory methods used in hair follicle drug testing are similar or slightly modified versions of those used in more common forms of drug testing, like urine drug testing. Laboratory methods used in drug testing are generally categorized as initial or confirmatory methods:

  • Initial test methods: Immunoassays are a common method of drug testing but provide only preliminary results. Results include which drug or drug classes were detected above the lab’s cutoff for positive results. In order to reduce the risk of inaccurate results on initial testing, positive test results should be followed by testing using a confirmatory test method.
  • Confirmatory test methods: Confirmatory test methods, such as gas or liquid chromatography, provide more detailed results than initial test methods, including specific metabolites detected in hair.

Although cutoff values for positive test results are not standard in all laboratories, the Society of Hair Testing, an organization that promotes research in hair testing, has proposed the following cutoff values:

Are test results accurate?

Although hair follicle testing is an accepted form of drug testing, the results of this test can be affected by a variety of factors, including environmental exposures, hair composition, use of hair products, and even hair color. Additionally, some drugs attach to the hair more easily, like nicotine and heroin, while other drugs are more difficult to detect in hair. Factors that affect test results include:

  • Environmental exposures: Inaccurate results can also occur due to environmental exposure to drugs. For example, during ​​exposure to secondhand smoke from cocaine or tobacco some of the smoke or vapor can enter the hair and lead to a positive test result. Washing hair samples prior to testing may not remove all of the drug residue from an environmental exposure.
  • Hair color: Hair color can also lead to inaccurate or biased results of hair follicle drug testing. Drugs like cocaine, methamphetamine, and opioids may bind more easily to melanin in dark hair, leading to higher concentrations in hair testing.
  • Hair treatments: Hair treatments, including shampooing, coloring, relaxing, and bleaching the hair, can affect the concentration of drugs and drug metabolites detected during testing. Chemically treated hair may not be appropriate for testing, and untreated hair may need to be taken from another part of the body.

Other concerns about the accuracy of hair follicle drug tests include:

  • Lack of standard cutoff values: Although some organizations have proposed guidelines for the use of hair follicle drug testing, standard cutoff values for the concentration of drugs in hair samples is still being established.
  • Challenging to interpret: Hair follicle drug testing may be more challenging to interpret than other types of drug tests due to the many factors that may affect the interpretation of test results. For example, drug metabolites in a person’s sweat can travel up the hair shaft and may make it more challenging to determine when drug exposure occurred.
  • Hard to detect low-level use: It can be difficult to detect low-level or one-time drug use or misuse using a hair sample for drug testing. Use or misuse of some drugs must be relatively heavy in order for a positive result on hair follicle drug testing.

Do I need follow-up tests?

Follow-up testing after a hair follicle drug test depends on the test results and the purpose of drug testing. If only an initial test was performed, a confirmatory test may be ordered to confirm preliminary results.

If a drug test result is positive, a health care provider may ask questions to evaluate the patient for a substance use disorder or addiction. The health care provider may ask about the impact of drug use or misuse on a person’s health and social obligations, any history of attempting to reduce or stop taking drugs, as well as whether the patient uses drugs in dangerous situations. Regardless of whether a patient meets the criteria to be diagnosed with a substance use disorder, treatment is available for drug use and misuse.

Questions for your doctor about test results

Drug test results can be difficult to interpret and patients can ask their doctor or the testing facility about the meaning of test results. Questions about test results include:

  • Why am I being tested for drug use or misuse?
  • What is the detection window of this test?
  • What is the test result?
  • Who will have access to my test result or medical record?
  • Will I be retested in the future?


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