Marijuana drug test is conducted by use of blood, saliva, hair, and urine. Urine is the most common sample that is used for marijuana testing. Hair testing is considered as the second most popular method for detecting marijuana.

Hair specimens are analyzed for the presence of marijuana. The drug when enters into a body, gets converted into a metabolite. These compounds enter into the bloodstream and then reach hair. Then they get deposited in the hair follicles. Both the parent drug and its metabolite can be detected by screening the hair sample.

Hair grows continuously out of the follicle. Hence, any drug components that are present in the follicle appear in the hair strand. Marijuana drug test using hair samples is done at workplaces. This helps in checking the presence of marijuana or its metabolite. However, it is not possible to know the content of the drug that is present in the hair strand. However, for confirmatory tests advanced technology such as gas chromatography and mass spectrometry are used.

Hair testing can be done easily at any place. There is no issue of privacy. The sample can be collected and administered easily. Hair can be taken from any part of the body including head, armpit, chest, and legs.

When compared to urine, blood and saliva tests, hair testing is able to detect the drug for a longer period of time. The drug can be detected for as long as 90 days using just 1.5 inches of hair sample. One of the advantages of hair testing is that the sample cannot be adulterated or substituted. However, this method is most expensive when compared to others. Hair test kits are also available. They are also expensive as they require a laboratory for getting the result.