How Long Does Marijuana Stay in Your Hair Follicles?

This article about Medical Marijuana was published on and updated on December 9, 2019 . Medical facts in this article was checked and article was medically reviewed by our author , who is expert in Medicine.

The simple answer is a long time up to a period of 90 days after your last use of marijuana products.

How Does Hair Testing Work?

Hair samples are taken by cutting about 100  samples from close to your scalp to 1.5 inches from the scalp. Once your hair is collected, it’s washed to remove any external contaminants, chopped up, and then digested in a solution that breaks it down into its components. The sample is then tested using an immunoassay test.

In the case of a positive test, another sample of the same hair is usually put through a secondary analysis that uses techniques called gas chromatography and/or mass spectrometry.

What Can a Hair Drug Test Detect?

What can be detected in hair tests for drugs? Hair can be tested for THC as well as for THC metabolites such as 11-OH-THC and THC-COOH. Hair drug tests are known to give false-positive tests for pot products due to environmental contamination and one report said that we should not rely on hair drug tests for THC at all. A 2015 scientific study concluded that THC does not primarily get into the hair by way of the bloodstream but first gets into a sweat and then is transferred to the hair externally. The importance of false positives in child custody cases was recently emphasized.

To avoid this problem, it has been proposed that testing hair for THC-COOH and 11-OH-THC should be done instead of testing for THC because the former two compounds are made within the body and cannot come from external contamination. A 2019 study recommended that approach.

Hair drug tests can also identify other drugs such as opiates, cocaine, PCP, methamphetamines, and Ecstasy.

What Are The Hair Follicle Drug Detection Times?

As mentioned, weed products can be found in hair up to 90 days after a single-use. Hair grows at the rate of about ½ inch a month so thus it can take as many as 90 days and there will still be THC in hair samples that are 1.5 inches long but a 2019 study found THC-COOH in hair samples as long as 6-7 months after discontinuing Cannabis usage!

Which Employers Use Hair Drug Detection Tests?

Hair testing for marijuana products is sometimes used in the transportation, construction and manufacturing sectors and in legal situations such as child custody cases and for monitoring of individuals in parole or probation situations. Hair testing cannot be used for employees covered by the DOT or for most other federal employees

Some companies, particularly those who are short of qualified employees may choose either to not test for Cannabis or to ignore test results.

How To Pass a Hair Drug Test?

How can you beat a hair follicle drug test? For years the Macujo and Jerry G methods have been recommended as ways of passing hair drug tests. They both involve complicated chemical treatments to clean and wash your hair but no amount of hair follicle drug testing shampoo or washing according to some sources will detox your hair sufficiently to allow you to beat a hair test. It has been claimed, however, that bleached hair does not retain metabolites as well as dark or unbleached hair and there are commercially available hair detox shampoos.

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