What time period does a standard hair follicle test cover?
A standard hair follicle screen covers a period of approximately 90 days, but is susceptible to time variation depending on the growth rate of your hair. The hair sample is cut as close to the scalp as possible and the most recent 3.9cm (or 1.5 inches) are tested. It is possible to go back even further than 90 days since the time period is limited only by the length of the hair sample, but is standardized to a 90 day history.
