A friend is in a Suboxone program but continues to use heroin about once a week occasionally he has come up positive after being clean for 5,6,and 7 days. he has very low body fat. Can anyone explain why this would happen when opiates should be undetectable after about 3-5 days? He said that he has even come up positive after 9 days clean? his program does not use instant tests but specimens are sent out to a lab. can this make a difference and other than testing yourself is there any way to make sure you will come up clean? Though he still uses once a week the suboxone has kept him from going back to a daily habit and i would hate to see him get kicked out of the program and go back to daily usage.