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Hair Sample Drug Test Information

Hair testing is a method of drug testing approved by the U.S. Food and Drug Administration. It is becoming increasingly favored by businesses and public agencies for pre-employment drug screening. Hair testing is generally more expensive than other types of drug tests, such as urinalysis or saliva tests, but it is more accurate, less invasive, and more convenient.

  1. Requirements

    • A hair test requires various strands of hair from the scalp, each at least 1/2 to 1 inch long. If scalp hairs cannot be obtained, body hair may be used instead. At least 40 mg of hair must be obtained in total for valid test results. The hair sample must be submitted to a laboratory and analyzed for drug use.

    Procedure

    • Various chemicals are applied to the hair sample to test for drug metabolites. If drugs have been used, the chemicals show the corresponding drug metabolites and indicate how long they have been in the body. The laboratory results are analyzed and interpreted as either "positive" or "negative" for the use of drugs.

    Drug Detection

    • Hair testing can detect five major classes of drugs: marijuana, cocaine, opiates, amphetamines and phencyclidine (PCP). If requested, additional panels can be added to detect the presence of heavy metals, poisons and toxins, and alcohol with a hair test. Hair testing is an optimal method for detecting long-term drug use because it can detect drugs used within a historical period of up to 90 days from testing.

    Reliability

    • The FDA-approved hair drug test cannot be fooled with detoxification products, such as shampoos, because only the inside shaft of the hair is analyzed. According to DrugTestingNetwork.com, hair tests provide "nearly twice the number of positives as urine testing," but they are not infallible because "after a drug is used, it takes about 7-10 days for the hair containing the drug to grow out of the scalp enough to be cut. Therefore, the hair test will not include drugs used in the week prior to the test."

    Confirmation

    • Hair tests use a process of confirmation that includes gas chromatography/mass spectrometry (GC/MS) in order to remove doubt about false test results. This is the same confirmation procedure used in forensic investigation and is therefore extremely precise.

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