The home tests dont work properly. I took one a week before I had my test i took a home one and I passed. Keep in mind I've only smoked a few times in my entire life. After that I didnt smoke again and nearly 20 days had passed since the last time i smoked and even then i hit the blunt 3 times. I took a home test the morning before I had my official test.. after I had drank about a gallon of green tea and a gallon of water and had taken about 4 asprin. I failed. I took another test that same morning about 2 hours later after even more water and more asprin and I failed. Went and took my official test, not pissing any more times.. all nervous and everything and passed.