hi there, I would like to help you.
Marijuana is actually not the one detected in the drug test but its metabolite... THC. If you smoke marijuana everyday likely chance it's going to be detected even up to 30 days from doing marijuana is still high.. however, if you stop and follow below, you might get a chance of ridding your body of the metabolite THC.
The first factor is metabolism. If you have a high basal metabolic rate (ie: if you're built like a cross country runner) then these metabolites will be removed from your body faster. The tricky thing about thc is that unlike most recreational drugs, it's fat-soluble. This means that metabolites will become trapped in fat cells and take a lot longer to be excreted from the body than water-soluble drugs. But, if you're slight of build, this means you don't have a lot of fat to begin with. People who have between 8% and 12% body fat will be the ones who say goodbye to those metabolites first. When you have fewer fat cells, you reduce the chance of free-floating metabolites in the blood fusing with fat cells. If you are both skinny and have a high metabolism (ie: you can eat a boatload of food and not gain an ounce) you're also lucky. The faster you burn energy, the faster you excrete wastes from these metabolic processes. So realistically if you have a low body fat content and have a fast metabolism, you could knock a week or two off that thirty day figure.
The second factor is exercise and water intake. Exercise causes cells to go into overdrive. Energy reserves are tapped into in order to fuel metabolic and energy requirements during intense exercise. Contrary to popular belief, you cannot "sweat out" the metabolites, but you can figuratively do so. The more cells are stimulated to provide a lot of energy, the more they'll need to excrete waste products. These waste products include THC metabolites. Water is also a crucial factor. As we've said before, THC and its metabolites are not water soluble. However, water is necessary for the proper functioning of all body cells. If you drink sufficient quantities of water, your cells will be able to work more efficiently and carry away waste much more quickly. So, if you engage in heavy exercise regularly and drink plenty of water, you will once again knock some days off that thirty day benchmark.
The third factor is use. Someone who only smokes once a month will be much less likely to fail a drug test than someone who smokes three times a day. The issue here is simple summation. If you smoke once a month, then metabolites from only one bowl/joint will be distributed throughout your body. Therefore, the chances of enough metabolites being present in the urine you give on the day of your test is comparatively low. On the other hand, if you smoke several times a day, you're potentially filling fat cells with a snowball effect. Since THC metabolites take longer to excrete than other metabolites, smoking regularly will keep adding more and more and outstripping the excretion rate. Therefore, if you only smoke once a month, your chances for passing a test are relatively higher.
A final note before my concluding remarks. Urinalysis tests are different from hair or blood tests. Hardly anyone will test your blood for THC metabolites, unless you're in a rehab program or perhaps applying for a government position. THC metabolites don't stay in blood for more than a couple of days. Urine is the most popular form of drug testing. All of the aforementioned factors I discussed are with regard to URINE testing. A hair test cannot be beaten. They are rare, usually only used by employers in certain education and government fields. But they are pernicious due to their mechanism. When you smoke, metabolites are circulated through your bloodstream and some end up in the nourishing blood vessels of hair follicles. These metabolites are then trapped in the keratin in the hair and cannot be removed by any lifestyle changes or commercial preparations (despite what internet ads claim!).
If you're skinny, can eat a cow and not get fat, run/bike/swim regularly, drink a lot of water, and only smoke marijuana once a month, then you can expect to see those metabolites gone from your system in as little as three days. If you're overweight, gain weight easily, don't exercise, drink more coffee than water, and smoke three times a day, then you can expect metabolites to be detectable up to and OVER thirty days. The painful fact is that the only way to be sure about being able to pass a drug test is to abstain from smoking at least a month before the test. Many of us don't have the luxury of knowing about a test this far in advance. The best you can do on short notice is to put your body through some hearty exercise, drink a lot of water, and STOP smoking until after the test. If you fail, you fail. Perhaps it'll be a learning experience or perhaps not.
I know it's lengthy but I hope I helped answer your question.
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Edited by Dr.PMT on 6/26/2010 at 2:31 PM EST