How long can heroin be detected in a lab test?

Most likely it will be in your saliva for about 72 hours. But you may be able to pass in 48 hours. All depends on how much you are doing and how long you've been doing it. I get them randomly and have passed in 48 hours but I only did it 2 days in a row roughly 2 bags each day. So it all depends but 3 days should be safe