actually i have smoked hours before using this method to pass a test. by all means us a home test to be safe. but at times i was gettin tested once a week and smoking daily and still passed. no cranberry juice, no niacin, no vineger, just water. several times i thought i was going to vomit from drinking so much water in such a short time and i felt like my eyeballs were floating. But i passed every test and stayed out of jail. one more thing these were the strip tests not laboratory tests and i have no idea how well it works with lab tests. but my little blue bars came up every time since 2000!