oral drug test for heroin?

[adzket]

hi gys wondering if anyone can help i have an oral test on monday at my doctors as i have been put on a methidone scrip and they need to check that i am takeing the methidone but not useing heroin. i am taking the methidone so this is not a problem but i am still useing heroin and need to no if there is a way i can fool the test i know they register heroin as have been tested befor and got positive i realy need to beat it as if i get possitive this time i will get thrown of my scrip any help whould be great. also how long does it take for heroin to get out of my system if i was not to take it roughly? thanks adz.