What does it mean if you pass a hair follicle test?

A hair follicle drug test detects drug use within five to 90 days of test administration, according to Health Street. Unlike urine tests, which can only detect drugs consumed within a week of the test, hair follicle tests are able to detect drug use patterns over a long time period.

Drugs enter the bloodstream after ingestion and are then metabolized, explains Health Street. The metabolites circulate in the bloodstream and eventually end up in the hair follicles. Hair follicle tests examine the first 1.5 inches of head hair, which represents about three months of hair growth, to determine drug usage. Drug users have difficulty evading detection when administered a hair follicle test.