Hair Drug Testing 101

Haley Bass

Hair drug testing or “hair follicle testing” is a very accurate and efficient way of screening for drug use. Whether you’re trying to screen potential candidates for a new job or you’re maintaining compliance with certain regulations, drug testing is often used in the workplace to keep employees safe and healthy. While most employers are familiar with using urine samples for drug tests, an increasingly popular testing method is hair drug testing.

Here are our answers to some of the common hair drug testing questions we’ve received.

How does a hair drug test work?

A hair drug test uses a hair sample, typically from the hair’s root, to screen for drug use. When someone uses drugs, the substance is absorbed into the bloodstream. Because each hair follicle has a blood vessel to feed the hair growth cells, the drugs are carried from the blood into the hair follicle. Traces of drugs can then be detected in the hair follicle.

What does a hair drug test test for?

Hair drug tests typically test for cocaine, marijuana, opiates, methamphetamine, ecstasy, and PCP.

What is required for a hair drug test sample?

A single hair isn’t going to be enough for a hair drug test, and you can’t use hair collected from a brush or another source - it must be taken directly from the person’s head. For the analysis to effectively determine drug use, a sample of hair needs to be 1.5 inches long, and have the thickness of a pencil.

Why would an employer choose hair drug testing over other sample options?

While there are several sample options for drug tests, an employer might prefer hair drug testing because:

  • There’s a long detection period - usually up to 90 days
  • It’s a relatively noninvasive collection process
  • If an employee briefly abstains from drugs, it typically won’t affect the results
  • It’s very difficult to cheat a hair drug test, making results more accurate
  • There’s also greater result accuracy because a lab can retest the same sample multiple times

What are the downsides of a hair follicle test?

Although there are a lot of positives to hair drug testing, it isn’t nearly as popular as urine drug testing. There could be several reasons for this, including:

  • Hair drug tests are more expensive than other test methods
  • While hair samples can detect long-term drug use, they can’t detect recent use
  • There’s a longer processing time required to get results

What if the person being tested has no hair?

When someone has short hair, the sample can still be collected, it just has to cover a larger portion of the head. If a person is bald or has a shaved head, a body hair sample can be collected. If the person being tested has no hair on their body, a hair drug test cannot be administered.

Are there ways to cheat a hair follicle test?

A hair drug test is nearly impossible to cheat. Even if someone uses certain shampoos or products that claim to cleanse hair follicles, they’re unlikely to remove the drug metabolites. Because the sample is often collected in person, it would be very difficult to attempt a sample substitution.

How far back can a hair drug test detect drug use?

Hair drug tests have the longest detection period, and can typically detect drug use for up to 90 days. Depending on the drugs used, a hair sample can sometimes help determine when drug use occurred and whether it’s been discontinued.

Concentra offers a variety of drug testing solutions, including hair drug testing, to help keep your workforce safe and healthy. To learn more about our drug testing program, talk to one of our work health experts.