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Hair Drug Test- Myths & Facts


Hand cutting hairWhen it comes to drug testing, you need to know each of the facts: Does it work? How far back does it go? Which types of drugs can be detected? Let's talk about some common facts and misconceptions concerning the hair follicle test.

How far back does it go?

Hair drug testing goes back much further than urine drug testing. As a matter of fact, when you ingest a drug, drug indicators can go into a strand of hair and stay there forever. If you think about it, hair grows at an average of .5 inches a month. Therefore, if your hair is 18 inches long, and you test at the end of the hair strand, drugs could be detected in your hair for the next 3 years. No need to worry though, there is only one standard for this test: 1.5 inches of hair, cut from the root. This will be detect approximately the 2 previous months.

Why trust a hair follicle drug test?

First and foremost, it is nearly impossible to cheat. Our hair is something that we can’t cover up. The consumption of drugs will always show accurately when tested from our hair, whether that be head hair or body hair. Although it can't be covered up, there are a few popular myths that have people thinking the opposite. For example, users cannot use a special shampoo to cover it up. Also, contrary to common beliefs, second hand smoke will not result in a positive drug test.

Body hair vs. Head Hair?

Although similar, there are a few differences. Here are the facts:

  • 1.5 inches of hair is needed for the standard 90 day drug test. If head hair it too short, body hair can be used.
  • Although there is no released research or tests, it is suspected that the body hair test can be detected much further back, as far back as a year.
  • The results will not and can not detect the specific day of drug use.
  • While urine tests can detect only one recent use, hair follicle tests can detect use over time.

When are DOT Tests Conducted?

There are a number of situations when DOT employees may be subject to drug testing. The most common situations include pre-employment screening, reasonable cause, random tests, post-accident, return-to-duty testing, and follow-up tests.

For more information on hair follicle drug testing contact us today or give us a call (210) 361-7778or learn about some of our other drug tests: