How long will drugs stay in my hair? Hair testing should always be head hair if at all possible for best results. 1.5 inches of hair provides best results. Our labs detect drug use up to 90 days with head hair. Hair shorter than 1.5 inches may provide a shorter window of detection as it is typically 30 days look back for every ½ inch of hair. Specialty testing may be available at certain labs we work with for longer hair or to break testing down into increments of ½ inch head hair for 30 day period look back results; specialty testing is more expensive.
With body hair, the look back period is up to 90 days. It is possible that there could be a longer look back period but there are no conclusive studies and no way to give an exact look back period. You can be confident with body hair of a 90 day lookback period.