How accurate are urine tests for marijunan?

There are so many different opinions when it comes to how long marijuana can be detected in urine but I'd like to know if anyone knows how the urine test actually works? Meaning, a great deal of whether or not marijuana is detected depends on the test. So are these test super thorough like that? And isn't there a level or something that they use to detect it? Like there is a limit on the amount to be considered negative?

no, any marijuana can be seen on the test they put it through. if you gain a lot of weight after using marijuana, your fat cells will store it and you might have a chance of passing the test

Present urine screens are very sensitive for Canabis and can detect it up to 6 months after smoking it or ingesting it. Every time you do weed it resets that 6 month clock. So, if you are looking to pass a "wizz-quiz" you better be clean for six months.

Also, keep in mind that most employers who require urine drug testing for employment, also require drug testing if you go to the ER for a work related accident. Some even require random testing!

well
my best friend smoked three weeks ago an got tested two days ago an passed.
yeah miracle i know, thats what i said
but she said all she did was drink an a$$ load of water..

so..
[: maybe youll get luckyy

When the manufacturer's instructions are followed, urine samples containing at least the stated detection level of 9-carboxy-THC will test positive at least 95% of the time. In a CDC field-test survey of 64 laboratories, those using the SYVA system for urine screening for cannabinoids had an incidence of 4% false-positive results (2); whether these errors were analytical or clerical in nature was not determined. The manufacturer states that any positive test result should be confirmed by an alternative method go to this site it will explain in whole http://www.cdc.gov/mmwR/preview/mmwrhtml...

They are accurate, but you can dilute your urine down enough to where its like 98% water which results in there basically being no trace of marijuana in it. That's easily done by drinking boat loads of water.

Common sense would tell you that water is not marijuana or any ingredient in it. So its not the accuracy, the test are accurate. Its just methods people use to circumvent the tests, like the one I mentioned, are working.