The California NORML website provides a detailed THC-level chart. It displays the potential amount of THC in a person's system after one use using a urine sample, as well as the potential levels of a person who uses marijuana regularly.
California NORML also provides a THC-level chart that displays potential THC levels from a blood test that is taken within hours after use. Depending on the type of test, the amount of marijuana, a person's metabolism, the frequency of use and other unknown factors all impact a person's THC levels.
The THC chart shown on the California NORML website explains how many drug-free days it may take a person to pass a blood or urine drug test. For example, a person who has only used marijuana one time may be able to pass a urine drug test after one day, but it could take up to seven or more days. That same person may be able to pass a blood test after only 12 to 24 hours. Those who use marijuana on a regular basis have higher levels of THC, making the time frame for passing a urine or blood test longer. These people may be able to pass a urine test any time between 7 and 100 days or more. A passing blood test may be possible after 2 to 7 days.