Today the NFLPA announced that the NFL's substance abuse testing period will begin in three weeks. Appropriately enough, -- or ironically, depending on how you look at it -- the start date is April 20th aka 4/20. That testing period will continue through August 9th which is right around the middle of training camp for most teams.
Marijuana is the most commonly used substance among those banned by the NFL. The three week warning should be plenty for any NFL players who enjoy a little toke now and again. Though, heavy users should probably stop smoking immediately.
Studies show THC from marijuana use can stay in the system anywhere from a few days up to two months in extreme cases. Though typically, for frequent users, it should be free from the system in about ten (10) days. That means it wouldn't show up in urination tests.
Yet, even knowing this, players still manage to pop positive on their urination tests every year. With three weeks warning and exact dates put out, it pretty much takes either a special kind of stupid or a serious addiction problem to pop positive for marijuana use.