I used this product today for my whiz quiz for my new job, and since it worked beautifully, I will recommend it to those of you who may need it in the future. I took it, and it takes 2 hours to activate... but you have to urinate quite a bit before you pee clean. So it says "pee 5 to 6 times," but just to be sure, I'd buy a few home tests. (If you get one just for marijuana, you can buy a 2-pack for $10 at some pharmacies) I haven't smoked in 2 weeks, and am not a heavy smoker anyhow, but just to be on the safe side, I bought this stuff. So the first home test I used, I failed. **Thank goodness I was being safe rather than just assuming I was alright** But I peed 3 or 4 more times and then I took the other 2 and passed them both... so I headed down to the clinic and voila! It's supposed to only work for 5 hours after the initial 2, so you are on a time limit... but still that's a large time bracket. So consider Vales. It also worked for my brother and he even smoked that morning!! (Not that I would recommend that... that's playing russian roulette!!) --luv mj--
