Hair drug testing is one of the most convenient methods to detect drug abuse. It is now gaining popularity among employers who conduct random on-site drug testing at the workplace or pre-employment screening. It is also preferred by parents who want to test their kids for drug use.

Court systems in several countries such as the United States, United Kingdom, and Canada also recognize the evidentiary weight of hair drug testing results. In the U.S., results from hair follicle analyses are legally and scientifically recognized under several established Rules of Evidence.

What is Hair Drug Testing?

Hair drug testing is a method used to determine whether the person being tested has a history of drug use. It typically requires at least 100 strands of hair that are cut at the scalp.

According to research, drug metabolites that run in the bloodstream are absorbed by the hair as it grows. Because long-term drug use produces metabolites or by-products that are absorbed into the blood and stored in the hair, this screening method allows for a longer detection window compared to other tests. It can detect drug use for up to 90 days from the last exposure, depending on the substance being tested.

Substances Identified by Hair Drug Testing

Hair screens can identify a number of substances. Some of the most common substances are as follows:

  • Amphetamines
  • Cannabis
  • Cocaine
  • MDMA (ecstasy)
  • Methamphetamines
  • Opiates
  • Phencyclidine (PCP)

The Pros and Cons of Hair Drug Testing

Like all other drug testing methods, hair follicle test also has its pros and cons. Knowing the pros and cons of hair drug testing will guide employers when deciding whether or not it’s a suitable drug testing method for their workplace.


Here are some of the benefits of hair drug testing:


The method is convenient and painless. The collection process does not cause any pain or embarrassment. All that has to be done is to cut off a hair sample from the head, as near to the root as possible, or from any part of the body.

Longer window of detection

The ingested drug is processed in the body where metabolites are produced. These remain in the bloodstream and, over time, are carried into hair follicles where they are deposited.

A hair follicle test can determine a history or pattern of drug abuse. Analyses of the hair samples can check for the presence of metabolites of certain substances even 90 days after the last ingestion.

Lower chances for cheating and adulteration

Compared to urine testing, there is a much lower chance for samples to be swapped. As such, the results from a hair screen are more accurate. Furthermore, because the metabolites are stored in the hair shaft, attempts to beat the test such as excessive hair washing and the application of bleaches or dyes are less likely to produce false negatives.

Easy storage

Hair specimens are easier to store and handle, than other fluids from the human body.


Like any other testing method, the procedure also has its drawbacks, which include the following:

Difficulty in detecting drugs taken recently

While hair screens are effective for assessing long-term drug use patterns, they may not detect drugs that were taken less than a week prior to the screening. The metabolites aren’t likely to be deposited in the hair follicles within such a short period.

More expensive

Hair drug testing methods are more expensive compared to urine and saliva drug tests. One reason is that it cannot be performed at home. Another is because more complex processes are involved in analyzing the samples.

Longer waiting period

Hair analysis takes longer compared to other screening procedures. It may take 2 to 3 days before the results become available.

Drug usage dependent on the length of hair sample

According to studies, hair grows on average of 1.4 cm per month. Hence, laboratories usually use at least 1.5 cm of the hair from the root end during the testing process to assess the donor’s 90-day drug use history.

While an employee drug testing policy is an important tool to keep workplaces drug-free, it is also very important for every organization to ensure that the drug testing method used by employees is convenient and easy. Organizations should also choose hair drug testing kits that are approved by the Food and Drug Administration (FDA) to ensure accurate results.

How A Standard Hair Drug Testing is Done

To conduct a hair drug test, a sample of hair is first collected from the person to be tested. The samples can come from the hair on the head or body hair.

Typically, more than 100 hair strands are necessary for analysis. This much is needed because hair growth is not consistent. Amounts fewer than this may not produce accurate results.

The sample is then sent to a laboratory to be examined for the presence of substances. It is washed to remove any secondhand sources of drugs. Then, it undergoes an initial screening process called enzyme immunoassay (EIA) technology.

If the sample tests positive, it undergoes a confirmation test where the laboratory uses highly specific chromatographic techniques to verify the presence of drug metabolites. These procedures include GC/MS (gas chromatography-mass spectrometry) and LC/MS (liquid chromatography-mass spectrometry).

When both the screening and confirmation tests return positive results, the hair test is reported to be positive. On the other hand, samples that yield a negative result during the initial screening are discarded and reported as negative.

Hair Drug Testing Products

Some home test kits allow the collection of the hair sample and provide for a package within which the specimen can be sealed. The sample is then mailed to an accredited laboratory where it undergoes testing and analyses. Some parents use these kits to screen their teens for possible drug use.

Here are a few of these home test kits:

HairConfirm 7 Panel Hair Follicle Multi-Drug Testing Kit

This test kit comes with materials that can be used for sample collection such as a collection foil, specimen pouch, and I.D. card. The HairConfirm laboratory can test for marijuana, cocaine, amphetamines, methamphetamines, opiates, ecstasy, and phencyclidine. The results are made available within two business days after receipt of the sample.

HairConfirm + Prescription Drugs 12 Panel Hair Follicle Multi-Drug Testing Kit

This product includes the same materials as the 7-Panel Hair Follicle Multi-Drug Testing Kit. What makes this product different is that aside from testing for the 7 major drugs, the hair sample can also be used to detect the presence of 5 prescription drugs (Vicodin, Lorcet, Oxycontin, Percocet, and Dilaudid). The results are also available within two days from receipt of sample.

5 Panel Laboratory Hair Drug Testing Service

This is a lab-based hair drug testing kit intended to be used for pre-employment screening. The purchaser is allowed to select his nearest testing facility and hair collection is arranged at the testing center.

The laboratory can analyze the hair sample for the presence of metabolites of drugs such as marijuana, cocaine, amphetamines, benzoylecgonine, opiates, and phencyclidine. The results are usually available within 5 to 7 business days from sample collection.

Frequently Asked Questions about Hair Drug Testing

Most people have several questions regarding hair drug testing. Here are answers to some frequently asked questions, which have not been covered by the information discussed above:

Q: How much hair is needed for a drug test?

A: As to length, the minimum is half an inch. Head hair grows at approximately 1 cm a month. So, the length of hair collected will determine the accuracy of the test. As for volume, about 100 to 120 strands are necessary. A sample of lesser volume may return false positive results.

Q: Where should the hair sample be taken?

A: It is preferable that the hair sample is taken from head hair which grows faster than body hair. The hair must be cut as close to the scalp as possible. The strands must be arranged in such a way that all the root ends are together. This allows proper analysis of the sample.

However, if the person to be tested does not have sufficient hair samples, a combination of head hair and body hair can be used for analysis.

Q: Can hair from a comb or hairbrush be submitted?

A: No. The hairs on a comb or hairbrush may not all be from the same period. The sample is also likely to be insufficient and will probably return inaccurate results.

Q: How is body hair collected?

A: Body hair samples can be taken from the underarms, arms, and legs. The length must be at least half an inch.

Q: How long does it take for drug use to be detected in the hair?

A: It takes about 5 to 7 days for the drug metabolites to be detected in head hair. This is the time that it takes for the hair to grow from the scalp. For body hair, it takes longer.

Q: What period is covered by a standard hair follicle drug test?

A: A hair follicle drug test is able to detect drug use for up to 90 days from the last consumption.

Q: Why are the hair samples washed prior to testing?

A: Hair samples are washed to remove possible contamination from other sources. Laboratories observe wash procedures that are approved by the appropriate agencies such as the FDA.

Q: Can external exposure to other drugs such as marijuana smoke or crack smoke affect the test results?

A: The wash procedures eliminate the effects of secondary exposure. In addition, the tests performed checks for the presence of both the parent drug and the metabolite. Metabolites are only produced by the body and therefore, will not be detected as a result of environmental exposure.

Q: Does hair color affect the results?

A: The color of the hair is determined by the amount of melanin in the hair. Hair color has no bearing on the drug test results.

Q: Can products such as cleansers, bleach, or dyes affect the results?

A: Testing laboratories check the presence of drugs or their by-products in the hair shaft. This means that no commercial substance (shampoos, dyes, bleaches, etc.) can alter or affect the results. In short, the test cannot be adulterated.

Q: What are the main differences between hair and urine testing?

A: First of all, the detection window for hair testing is longer. It can check for a pattern or history of use. Urinalysis can test for immediate use of a drug because it can only detect drug use for up to 48 hours.

Second, hair testing is difficult to adulterate compared to urine testing where the samples can be swapped or where a positive result can be avoided by changing the schedule of drug use.

Third, hair screens are more convenient and non-intrusive.

Q: How long are test results kept by laboratories?

A: Test reports are usually retained for a period of two years.

Q: What happens to the hair samples that were not tested?

A: Excess hair that was not tested is stored in the chain-of-custody envelope or pouch. The samples that returned a negative result upon initial screening are kept for a few months before they are discarded.


Some studies have shown that hair testing returns more drug use results than urinalysis. It has also been found to have more advantages compared to other screening methods. It is non-invasive, safe, convenient, and reliable.

Those who opt for this screening process should contact an accredited laboratory who can conduct on-site testing, laboratory testing, or screening of samples taken using home kits. These facilities have trained professionals and experts and can guarantee accurate and reliable results.

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