I could not swear to it but I spent some time in a court appointed out patient rehab where we had random drug screening with the color system and I had a friend in the program with me who I witnessed smoking marijuana many times who used niacin and as much water as he could gulp down in a few hours in combination with a multi vitamin and he passed his test in as little as 24 hours. I seen him pass a few test like that but this will not work if you have been smoking heavily I also seen him fail a test with the same method in the drug test passing business reframing from using is the only shure thing