Select a substance and how often it's used to see typical detection windows for urine, blood, saliva, and hair tests. Educational estimates from published clinical references.
Detection windows describe how long a test can return a positive after last use — not how long impairment lasts, which is far shorter for every substance listed. Frequency of use is the dominant variable for fat-soluble drugs like THC, where chronic use builds a reservoir in body fat that drains for weeks. Water-soluble drugs (cocaine, meth, most opioids) clear on more fixed schedules regardless of frequency, though heavy use extends them modestly. Hair testing is a different animal entirely: it reads roughly 90 days of history for nearly everything, detecting patterns of repeated use rather than single episodes.
If you're researching this because stopping has been harder than expected, that difficulty is worth taking seriously — our guides to cannabis detection, drug test types, and the treatment directory are good next steps.