From a different post I think I found on here :
I will tell you something that will help you out. I am a RN in one of the best hospitals in Az and i see many ppl come in and have to administer UA's. There is no guaranteed way to get thc out of your system. but there is a way to dilute your urine and still get a negative result. First off, this all depends on your BMI, if you have a high metabolism and weigh anywhere from 135-160 your chances of ridding your fat of THC are greatly enhanced. If any higher and you are overweight i recommend to just stop smoking, sorry no bad-mouthing intended. however if you fit into the high Meta. category here it goes. First off, dont smoke the day of your UA, and dont eat anything on that day until after the test. Drink vitamin b-complex(contains niacin). Buy AZO cranberry pills to clean your urinary tract, drink G2 gatorade all day(3-6bottles at least) 2 30min b4 the test.. Take 1 vitamin b comp. in the morning w/2 azo's. urinate frequently..take 1 more vitamin-b comp.w/2 G2 gatorades 30-45 min b4 the test to make your pee yellow and full of natural urinary excretions, consider intake of creatine for 2-3 days prior to the test(it will metabolize to creatinine in about 24-48 hours) and will come out normal the day of the test even if diluted. Thats about it...Good luck..