Urine drug testing is the most frequently used method of all, making it the most relevant to you to know how to deal with it. It also has a longer detection time than a saliva test and is inexpensive to perform. For urine tests, weight, body fat, the amount of marijuana used, and how frequently you used marijuana all factor into how long the THC will remain in your urine.
After just a couple of hours from when you last smoked, THC appears in your urine. Without taking weight or body fat into account, a person who has used marijuana just once in their life will have a positive urine test for between 1-6 days. Whereas an infrequent user will show for 7-13 days, while a frequent user 2 weeks or more, and a heavy user for a month or longer. The longest anyone has reported is between 45 and 90 days after they stopped smoking. This applies only to the heaviest of pot smokers.
Technically urine tests check for THC metabolites rather than THC itself, which is the reason it can detect them in your system for a much longer time. The difference is that THC is the active ingredient that makes you feel high. THC metabolites, or THC-COOH, on the other hand, is the chemical that forms as the liver breaks down the THC. It remains in the for much longer periods of time than THC itself.
Passing a urine test
There are lots of methods employed by marijuana users who need to pass a marijuana test. Some work, others probably don’t at all. Some products called ‘urine cleansers’ are worthy of the skepticism surrounding them. You might as well drink a lot of water or other liquid just before the test, as it is a natural way to dilute the urine anyway. Proceed with caution, however; if it is too diluted, then the lab will reject it because it is unable to properly analyze the sample. Potentially it could be a solution to a tricky situation where you just need to buy yourself some time. This could work, assuming you would be allowed to do a retest (and haven’t smoked since your first urine sample).