well, at three weeks, your system should be pretty close to clean. Your hair will remain dirty for awhile, 3-6 months or so. If you need to pass a whiz quiz right now, you have a few options. First, and most recommended, is using a product called quick fix. It is synthetic urine that has a heating pad and temp gauge and works everytime. Second, you can buy one of those drinks from a headshop. Since you have been cool for 3 weeks, those will probably work because they dilute your urine and you probably have low amounts of thc as it is(remember to take a bunch of vitamin B or multivitamins before hand in order to keep your urine yellow otherwise they could call the results inconclusive). If you don't have money to spend on the drink, you can always use a diuretic like cranberry juice to essentially do the same thing. If you are still worried, try purchasing a product called certos from you grocery store. It is for making gelatin. Mix it with some water and drink it and then drink cranberry juice. The certos covers you insides and the cranberry juice rinses you quickly. Remember, take the vitamins too and if you have to use these products also remember that when you begin to urinate, don't put the first part in the cup because that is where you will have the highest concentration of THC in your urine. Well good luck
Also, everyone says to drink water, that only works to flush you out right when you take a test. The THC stores in your fat cells in your body and takes time to metabolize. There is no quick solution to fix that. Just time.
And oh yeah, the person who wrote that poppy seeds has trace amounts of THC may very well be the least smart person on all of yahoo because that is just not true. Poppy seeds can lead to a false positive for opiates. Please, do society a favor and don't reproduce
I am not a doctor, but I play one on TV