Heroin is diacetylmorphine. It is considered a pro-drug (i.e. It sets the stage...) for morphine. Once heroin hits the brain it is converted into morphine, 6-monoacetylmorphine, and 3-MAM. Other drugs that contain morphine as a metabolite are morphine and codeine. 6-MAM is a metabolite unique to heroin and if it's in your urine, it's indisputed that that was the drug used. However, 6-MAM only remains for about 24 hours whereas morphine will remain for 2-4 days. This can only be determined by a specific test called GC/MS but this type of test is employed for pre-employment drug screenings. Tests used by courts or for hometesting, like dipsticks, will just reveal it as "opiate" which could mean codeine, morphine, heroin, hydrocodone, oxycodone, hydromorphone, oxymorphone, nicomorphine/codeine, dihydromorphine, 6-MAM, plain old opium, and possibly fentanyl, methadone, and meperidine among others that your opiate receptors respond to. Also, Mythbusters proved that just two poppy seed bagels will cause a positive opiate test (as they contain enough morphine and codeine to put you just over the threshhold). So with the dipstick test, maybe you had a couple of bagels... Or maybe you're mainlining heroin.
