How long does morophine stay in your system?

Half life and more: That depends on that you mean by "your system." the "half life" of morphine (the time it takes once it peaks in the body for half of it to have been metabolized) is about 2 hours. But it takes about 3 days to eliminate 85% totally from the body for an average person's liver. That said, its metabolites are detectable in a urine test oftentimes for a week, and in a hair test almost permanently.