Marijuana (continued)
Although later and more reliable research has concluded that THC is retained at testable levels for much shorter periods of time, the 30 day timeframe continues to be repeated in much of the current literature. For example, a recent article in the MedTox Journal entitled Drug Testing Tutorial contains the following chart discussing the types of substances that can be tested for using urine and other bodily fluids, including the testing periods:
Detection Periods
Drug |
Urine |
Occular/Blood/Saliva/DAR |
Marijuana Single Use |
up to 3 days |
1-2 days |
Marijuana Multiple Use |
up to 29 days |
1-2 days |
Cocaine |
up to 3 days |
1-2 days |
Heroin |
up to 5 days |
1-2 days |
Morphine |
up to 3 days |
1-2 days |
Amphetamines |
up to 10 days |
1-2 days |
PCP |
up to 8 days |
1-2 days |
PCP Multiple Use |
up to 28 days |
1-2 days |
Barbiturates |
up to 16 days |
1-2 days |
Benzodiazepines |
up to 12 days |
1-2 days |
Note that the chart refers to the detection marijuana for a period of up to 29 days for chronic users. Although the chart is a valuable illustrative tool, the marijuana detection period appears to be based on older research. An excellent in-depth discussion of the latest research on this topic can be found by reading the National Drug Court Institute Drug Practitioner Fact Sheet entitled Urine Drug Concentrations: The Scientific Rationale for Eliminating the Use of Drug Test Levels In Drug Court Proceedings.
This Fact Sheet discusses our continued use of the following inquiries in the court/supervision arena:
Has the urine drug level increased or decreased since the last test?
How positive is he/she?
Does this level indicate relapse?
The level continues dropping so that indicates continued elimination, correct?
If any of these questions are being asked, it is almost certain that urine drug levels are being used inappropriately in the court’s decision-making processes. The Fact Sheet concludes that we should be using drug testing to determine the presence or absence of illegal substances, but the numerous variables associated with levels of concentration preclude an accurate assessment of how recently the use occurred, or the level of use. Further, the most recent research indicates that, depending on testing levels, most court ordered urine tests can only detect recent marijuana use for 3-5 days for occasional users, or up to 7-10 days for chronic users. Most testing facilities used by courts employ a 50 ng/mL cutoff level; if you're testing facility employs a 20 ng/mL cutoff level, you may be able to detect recent use for up to twice as long. For a detailed discussion see National Drug Court Institute Drug Practitioner Fact Sheet.