This question is usually asked in the context, How long after use will someone test positive?  Heroin is rapidly metabolized to 6-acetylmorphine, and 6-acetylmorphine is rapidly metabolized to morphine.  Heroin is rarely if ever detected in urine after heroin use.  6-Acetylmorphine may be detectable in the urine for 2-8 hrs after heroin use. Morphine is detectable in urine … Read more