This is the question that I get asked most frequently.  Why does marijuana stay in your system longer than the stoners who wander around in the parking lot long after the concert has ended?  Well the answer is not that complex.  Marijuana is a natural substance not a man-made substance.  Your body doesn’t reject it like it would reject a manufactured substance.  The residue from marijuana is a sticky substance that adheres to your lungs after you have inhaled it.  This residue takes a long time for your body to break it down and is released into your bloodstream at a slow pace. 

How long marijuana stays in the body system depends on the individual and the potency and amount of marijuana taken. You should therefore start by getting a Home Drug Test Kit to determine how long the drug stays in your own body system. If you know how long it stays in your body, you will know when to stop smoking pot before an upcoming test. You can also flush THC out of your system ahead of the test by drinking plenty of water and urinating as frequently as possible.
THC are stored in fat cells. Engaging in physical exercise while flushing your system will help burn some fat and release much more THC into your blood system and subsequently into your urine to be flushed out of the body before the test. The burning of fat should however stop well ahead of the time for the test so as not release THC metabolites without having the time to flush them out.

There are many mitigating factors involved in how fast these THC metabolites are expelled from the human body.  Everyone has a different metabolism so how fast you break things down has a lot to do with how fast the THC leaves your system.  Your body weight is also a key factor.  The heavier a person is then the more fat cells they have.  Hence, it will take longer for their body to get rid of the THC metabolites.  Another factor to the length of time marijuana stays in your system is the frequency of your usage.  If you constantly smoke, you are not allowing your body to process the metabolites out of your system so they are piling up like leaves falling to the ground in the fall.  The potency of the marijuana also has an effect on the length of time it stays in your body.  If you lead a sedentary life with little or no exercise you are not burning fat cells quickly so it will take longer for your body to get rid of the THC than if you exercise regularly and burn fat.

A common misconception is that if you drink a lot of water you will expel the THC metabolites quickly through your urine.  This is false.  Fat cells are not water soluble so you will just be going to the bathroom a lot with very little reduction in the amount of THC in your body.  This will result in some reduction but it will only reduce the levels of THC that hasn’t found its way into your fat cells yet.  You eventually will rid yourself of THC through excretions of urine, sweat or saliva but it takes time.