Does Hair Testing Work for Marijuana?

Hair follicle testing is used to screen a person for drugs. It is one of various drug testing methods used by employers, sporting officials, and law enforcement to obtain an accurate history of drug use. Unlike most other methods, such as urinalysis and blood testing, a hair follicle drug test can detect drug use for weeks or even months after the person has used, depending on the circumstances.

How Does It Work?

Hair follicles are small pieces of tissue that surround the root of a hair. It is embedded in the dermal skin layer. When a hair is pulled out, the follicle is often removed along with it.

  1. A lab technician cuts off a small portion of the person’s hair for testing (about 1.5 inches in length and about 1.4 inch. If the hair on the person’s head is too short, the technician can use body hair instead.
  2. The hair sample is placed in a sterile vial or specimen bag and sent to be tested.
  3. The first inch and a half of hair nearest to the root will be tested.

Hair testing is able to detect alcohol, opiates, barbiturates and various other drugs. A typical hair test looks at the 5 Panel drug screening.

Does Hair Testing Work for Marijuana?

Hair testing can effectively detect marijuana use for up to 90 days after use. Once the drug is in a person’s bloodstream, THC and the metabolites the body produces in response to it bind to hair follicles. These traces them permeate the strand of hair beneath the scalp as well.

Although it can take up to 10 days for this part of the hair to emerge from the scalp, it the part of the hair 1.5 inches from the head will contain THC and its metabolites for up to 90 days afterward.


Will My Hair Follicle Test Drug Will Come Up Positive?

If you searched the question, “Does hair testing work for marijuana?”, chances are you need to take a hair drug test in the near future.

Whereas urine tests and blood tests are used to detect recent drug use, hair follicle tests are meant to give information about a person’s lifestyle. It is possible to pass a bodily fluid test by abstaining from drugs for a short time, but not so with hair follicle testing.

If you have used marijuana in the past 90 days, there is a chance your test will be positive. However, this varies based on a number of factors, including how frequently you use marijuana (frequent users will have an even larger detection window), how fast your hair grows, and how your body metabolizer THC.

Note that in some cases, arriving at a hair follicle test completely shaven is considered a refusal to take the test.

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