Belgian_Tiger_Army
Debutant
My understanding is that meth amphetimes take at least 3 days to clear from the system naturally and that anything used to either speed that process or to mask it's presence from the test is also picked up in the testing.
Depends on what you use. The key is that you don't want to lower the specific gravity (?) of the urine - for instance by drinking too much water and diluting the urine.
There are other substances - available in the supermarket some of which are commonly used in detox diets - which you can take to shorten this to 24 hours if you aren't a hardcore (ab)user without affecting your urines specific gravity.
Then there are the more specialised products available which give you a window of opportunity where you are "clean" - for about 4 hours, but with maximised effectiveness at +3 hours.
The unlucky, fools, addicts and those who take substances that are fat soluble (I.E Marijuana) get caught.