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Updated on September 26, 2022
5 min read

Hair Follicle Drug Testing

What is a Hair Follicle Drug Test?

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

Hair testing identifies a variety of different commonly used legal and illegal drugs. The test requires a minimum hair length of 1.5 inches.

The benefit of hair testing is that it identifies drug use further back than other types like oral, blood, and urine tests. The results are reliable, in part because the process uses a follow-up test to confirm a positive result. 

Hair drug testing is also less invasive than some other tests, including urine and saliva. Many people don’t like the idea of having their hair trimmed during the test. But it’s more comfortable than someone watching you, which is the case with urine drug tests. 

No drug testing method is fail-proof. However, hair testing is one of the most reliable methods

For example, the ELISA test delivers negative or positive results within 24 hours. 

The ELISA test, also known as enzyme-linked immunosorbent assay, is a biochemical test commonly used to detect antibodies and other proteins in the blood.

The second test (a GC/MS test) confirms the initial positive result and protects against false positive results. 

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

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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 a variety of 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
  • 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. 

As hair grows out, all drugs used are encased along the shaft. The longer your hair, the longer back the test can find evidence of drug use. This is why people cut their hair to avoid a positive test result—but this method is not foolproof. 

One of the benefits of a hair drug test is that there is less of an opportunity for test subjects to “cheat.” But it’s possible to alter a urine or saliva test. 

There’s not much you can do to your hair that alters its structure in terms of drug testing. Dyes, hair products, and shampoos don’t affect results. This makes hair testing very chemically reliable.

What Drugs Can Hair Follicle Tests Detect? 

Hair follicle tests detect several drugs, including:

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

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What Drugs Can Hair Follicle Tests Not Detect? 

What drugs are detectable and undetectable in a hair follicle test depends on the type of panel.

For example, a 5 panel test looks for marijuana, cocaine, PCP, opiates and amphetamines, but nothing else.

Higher panel tests are more specific and target other substances. These tests detect the same type of drugs as typical 5, 7, 10, and 12 panel urine tests.

What to Expect Before, During & After the Test

Hair follicle testing is easy and non-invasive. It usually takes place in a lab or medical setting. Some tests are performed in the workplace. Washing, styling, or dying hair does not affect test results.  

During the test, the technician or collector will cut approximately 100 to 120 hairs from the crown of your head. 

The hair can be collected together or from different spots to avoid creating a bald area. Body hair is used if there is not enough hair on a person’s head.

Once collected, the hair is placed in foil inside of a secured envelope and submitted to the testing lab. 

One of the benefits of hair drug testing is that there is less risk of corruption of the test sample. It’s easier for something to happen to contaminate a liquid sample like urine or saliva than it is for something to corrupt hair. 

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.

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How to Interpret Test Results

Negative hair test results from the phase 1 ELISA portion of the drug test are available within 24 hours of submitting a sample. 

A negative result in phase 1 means no further follow-up testing is needed based on those results. Negative results mean the test subject has not used any of the drugs tested for in the last 90 days.

If the initial ELISA test is positive, there will be a follow-up GC/MS test. This confirms the initial positive result and identifies the specific drugs present in the sample.

Very occasionally there is an inconclusive result. This typically occurs as a result of someone in the sample gathering or analysis chain not following proper procedures. 

In some cases, the sample is rejected completely due to improper collection. In these cases, a follow-up test will likely be ordered. If this occurs, you’ll be asked to take the test again. Because of the removal of hair, you might be offered the opportunity to take another type of drug test.

Test results are delivered to the test subject and/or the organization requesting the test via confidential means.

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Updated on September 26, 2022
6 sources cited
Updated on September 26, 2022
  1. Hadland, Scott E., and Sharon Levy. “Objective Testing.” Child and Adolescent Psychiatric Clinics of North America, vol. 25, no. 3, July 2016, pp. 549–565, 10.1016/j.chc.2016.02.005.
  2. Sharma, Gaurav, et al. “Hair Analysis and Its Concordance with Self-Report for Drug Users Presenting in Emergency Department.” Drug and Alcohol Dependence, vol. 167, Oct. 2016, pp. 149–155, 10.1016/j.drugalcdep.2016.08.007.
  3. Saitman, A., et al. “False-Positive Interferences of Common Urine Drug Screen Immunoassays: A Review.” Journal of Analytical Toxicology, vol. 38, no. 7, 1 July 2014, pp. 387–396, 10.1093/jat/bku075.
  4. Koster, Remco A., 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, vol. 36, no. 2, Apr. 2014, pp. 234–243, 10.1097/ftd.0b013e3182a377e8.
  5. P, Kintz, et al. “Hair Analysis for Drug Detection.” Therapeutic Drug Monitoring, 1 June 2006,
  6. Gryczynski, Jan, 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, vol. 141, Aug. 2014, pp. 44–50, 10.1016/j.drugalcdep.2014.05.001.h

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