Definition - What does hair follicle drug testing mean?
Hair follicle drug testing is a method used to detect the presence of drugs in a shaft of hair. When a person uses drug, the chemicals in the substances are are metabolized by his or her body and circulated through the blood stream. These substances are referred to as drug metabolites. These metabolites are eventually deposited in the follicles of the hair and become embedded in the person's hair as it grows. For this reason, hair follicle drug testing can detect drug use over a longer period of time than other drug testing methods. Hair follicle drug testing may also be referred to as hair drug testing.
SureHire explains hair follicle drug testing
To conduct hair follicle drug testing, most labs request a sample equal to about 100 milligrams of hair. The collector of the hair sample is asked to cut the hair close to the scalp and arrange the strands in a bundle for delivery to the lab for testing. Many labs ask that a minimum length of hair be provided. If scalp hair is not available, body hair may be used. However, only hair from the scalp can be used to determine a time frame if drug use is detected. This is because body hair does not grow at a consistent rate. A 1.5 inch sample of hair taken from the head will reflect drugs used by the test subject for an approximately 90 day period. Hair drug testing will not detect drugs used immediately prior to testing. It takes seven to ten days for the drug metabolites to enter the blood stream and for the hair shaft to clear the surface of the scalp, although hair growth rates vary from person to person and on different parts of the body.