This simple graph shows how long different drugs remain in your blood
Business Insider has produced this fascinating graph detailing the amount of time various legal and illegal drugs remain detectable in your blood. Most drugs are no longer detectable after a couple of days. The giant exception is marijuana, which remains detectable for two whole weeks.
One of the troubling implications of this disparity is in the context of prison drug-testing regimes, where the much higher risk of detection of marijuana use creates an incentive for those who wish to use drugs to switch to more dangerous substances.