Updated on April 3, 2024
5 min read

What You Need to Know About Hair Follicle Drug Tests

What is a Hair Follicle Drug Test?

Hair follicle drug testing uses a hair sample to identify drugs in a person’s body. It’s a newer testing method favored by the court system and employers.

A hair follicle drug test can detect drug metabolites, which are the byproducts formed when drugs are in your system. The test requires a minimum hair sample length of 1.5 inches from the head. Body hair can also be collected if necessary.

Hair testing can identify various drugs, including illicit and prescription medication. Compared to other drug tests, Hair follicle drug tests have a larger detection window which can aid in identifying drug use patterns.

How Do Hair Follicle Drug Tests Work?

The hair follicle drug test uses two testing stages to avoid false positives. The first test is the ELISA test, also known as an enzyme-linked immunosorbent assay.

It's a biochemical test commonly used to detect antibodies and other proteins in the blood. Confirmation testing is done using GC/MS if the result is positive.

The GC/MS, which is short for chromatography-mass spectrometry, is an analytical method that combines gas-chromatography and mass spectrometry. It can identify different substances within a sample, confirming the initial test results.


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How Long Can Drugs Be Detected in a Hair Follicle Test?

How long drugs are detected by a hair follicle test depends on various factors. Different drugs are detectable for different lengths of time. 

Timeframes are also dependent on:

  • How much of a drug was used
  • How quickly your body metabolizes the drug
  • Physical activity
  • Method of consumption
  • Age
  • Tolerance
  • The potency of the drug

Hair follicle testing can go back six months or more. It shows all controlled substances used in a timeline along the hair shaft. 

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What Drugs Can Hair Follicle Tests Detect? 

A hair drug test can identify drug use and the presence of specific drugs like:

  • Amphetamine
  • Cocaine
  • Ecstasy
  • Methamphetamine
  • Opioids, including codeine and morphine
  • Phenylcyclohexyl piperidine (PCP)

What Drugs Can Hair Follicle Tests Not Detect? 

What drugs are detectable and undetectable in a hair follicle test depends on the panel type. For example, a 5-panel test looks for substances like:

  • Marijuana
  • Cocaine
  • PCP
  • Opiates
  • Amphetamines

However, it can't detect anything else. Higher panel tests are more specific and target other substances. These tests detect the same drugs as typical panel 5, 7, 10, and 12 urine tests.

Furthermore, some substances may not be detectable with a standard panel. These include:

  • New substances
  • Synthetic drugs
  • Some prescription drugs

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How is a Hair Follicle Test Conducted

A hair follicle drug test is typically done in a lab or medical setting. However, some tests are performed in the workplace. In case of a workplace accident or suspicion of drug abuse, you can be subjected to immediate hair drug testing

During the test, the technician or collector will cut approximately 100 to 120 hair samples from the crown of your head. This can be collected from different spots to avoid creating a bald stop.

The entire process is easy and non-invasive. After collection, the hair is packaged securely in foil inside a secured envelope and sent to the lab for analysis.

How to Interpret Test Results

If you receive a negative result from the phase 1 ELISA portion of the drug test, you haven't used any drugs tested in the last 90 days. A follow-up test isn't necessary because there are no drug metabolites in your system.

However, if both the ELISA and the GC/MS test results are positive, that confirms the presence of specific drugs in the sample. The positive test result is then delivered to the test subject and/or the organization requesting the test confidentially.

What Happens if the Test is Inconclusive?

Occasionally the results of the test can be inconclusive. This can happen if someone in the sample gathering or analysis chain doesn't follow proper procedures.

Sometimes, the sample is rejected and a follow-up test will be ordered. You'll have to take the test again, but because of hair removal, you may be offered another type of drug test.

When a test is inconclusive, the entire body of data, including known history of drug use or prescription medication use, is reviewed in the context of clinical addiction medication. The goal is to determine whether or not you've been using drugs and to what extent.

What Can Affect the Results of a Hair Drug Test?

One of the benefits of a hair drug test is that you can't do much to cheat the test compared. As long as the identification of the test subject isn’t mixed up and no lab mistakes are made, there’s a good chance for accuracy.

Although some factors can affect the result, it isn't foolproof. These factors include:

  • Environmental exposure to drugs like second-hand marijuana smoke
  • Hair length and growth rate
  • Cutting your hair to avoid a positive result

There's not much you can do to alter your hair's structure. It's not affected by washing, styling, or dying.

Some claim that old-style aloe toxin rid or detox shampoo can remove drug residue from hair strands. However, this isn't true because the drug metabolites are embedded in your hair.

Benefits of a Hair Follicle Drug Test

The main benefit of hair testing is that it can identify drug use further back than other types of tests. The results are reliable because the process uses a follow-up test to confirm a positive result.

Hair tests are also less invasive than other tests like urine or saliva. Some people may be uncomfortable trimming their hair to provide a hair sample. But it's more comfortable than having someone watch you, which is true for urine drug tests.

Hair testing is one of the most reliable methods available. They're also a reliable method for pre-employment screening or workplace drug testing. However, hair drug test results may take longer depending on the test date and the lab's capacity.

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Updated on April 3, 2024
7 sources cited
Updated on April 3, 2024
  1. Hadland et al. “Objective Testing.” Child and Adolescent Psychiatric Clinics of North America, 2016.
  2. Sharma et al. “Hair Analysis and Its Concordance with Self-Report for Drug Users Presenting in Emergency Department.” Drug and Alcohol Dependence, 2016.
  3. Saitman et al. “False-Positive Interferences of Common Urine Drug Screen Immunoassays: A Review.” Journal of Analytical Toxicology, 2014
  4. Koster et al. “Fast and Highly Selective LC-MS/MS Screening for THC and 16 Other Abused Drugs and Metabolites in Human Hair to Monitor Patients for Drug Abuse.” Therapeutic Drug Monitoring, 2014.
  5. Cuypers E & Flanagan RJ. "The interpretation of hair analysis for drugs and drug metabolites." Clin Toxicol (Phila), 2018.
  6. Gryczynski et al. “Hair Drug Testing Results and Self-Reported Drug Use among Primary Care Patients with Moderate-Risk Illicit Drug Use.” Drug and Alcohol Dependence, 2014.
  7. Marrinan et al. "Hair analysis for the detection of drug use-is there potential for evasion?" Hum Psychopharmacol, 2017.

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