Cannabis Drug Tests

Cannabis and its active ingredient THC is tested for in most drug tests. After one-off or occasional use its break-down products or metabolites can be detected between 3-5 days after use. (1) However, THC can be detected in a chronic user up to 12 weeks after use (2) although the average is 25(3) -27 days (4).

Cannabis is highly detectable a long time after use because THC lingers in the fatty tissues of the body and leaks steadily into the blood and then the urine over weeks. It is difficult to determine exactly how long it will take the THC to leave your body. It depends on your metabolism, how much you ingested and how often you used weed or hash.

Marijuana Length of Time in System: Saliva, Urine, Hair

Testing for Marijuana and Hashish Use

Testing for the presence of THC is probably the most common drug test ordered. In most cases, a urine test is used for this purpose.

If the employer, court or other entity requesting the test has hired an agency to conduct the procedure, the first step in the process is to have the individual being tested go to a testing facility. He or she will be asked to remove their street clothing and put on a hospital gown. The idea behind this procedure is to minimize the chances of tampering with the sample.

The individual being tested may be asked to provide the sample in a dry room, which doesn't include any faucets or sources of water. If a restroom is used for the sample collection, the water to the faucets may be shut off at the main valve to prevent the subject attempting to dilute the sample with water. As an added precaution, colored water may be added to the toilet.

Once the sample has been obtained, it is sent to a laboratory for analysis. In the U.S., federal guidelines are used to determine whether this initial screening is positive or negative. A negative test result doesn't necessarily mean that no trace of the substance was found in the subject's sample. It only means the level detected was below the cutoff as set by the government as being high enough to be considered positive.

Positive Marijuana Screening by Usage Frequency

Usage Frequency
Estimated Detection Length
Usage at 1 time only 5-8 days
Usage at 2-4 times per month 11-18 days
Usage at 2-4 times per week 23-35 days
Usage at 5-6 times per week 33-48 days
Daily Usage (see Marijuana Addiction Signs) 49-63 days

Pot Testing Cutoff Levels

When drug tests are conducted, the unit of measurement is in nanograms per milliliter. When a urine sample is analyzed, a positive test is one where the subject had a level of 50 ng/ml of urine. If a person has a positive test reading, a follow-up test will be conducted to confirm the finding. For the follow-up test, a positive result is one where the level of THC in the subject's sample is 15 ng/ml. These are very small amounts, and it is possible for a person who is uses Mary Jane on an occasional basis to test positive for drugs.

False positives have been known to be triggered by consuming hemp-seed bars and other products, although the more detailed, more expensive gas chromatography-mass spectrometer (GCMS) test can tell the difference (5).

Second Hand Marijuana Smoke Positive Tests

In rare circumstances, passive smoking can cause false positives in urine tests, up to 4 days after exposure, although those who passively smoke have noticeably less concentrations in their urine.(6)

There is some controversy over whether the cut-off levels used to detect cannabis in blood and urine tests is too low, leading to a high degree of false positives, especially from second-hand smoke. If you feel your drug test is false due to passive smoking, then you may be able to demand that the threshold of your test be increased 65 ng/ml, not the 15 ng/ml of many laboratories. The higher level is thought to distinguish between active and passive smoking.

How to Pass a Marijuana Urine Test

Many people who are concerned about past exposure to marijuana, whether through active use or spending time with people who use this substance, are wondering how they can beat a drug test. There are sites online that recommend finding a way to substitute someone else's urine for the sample, drinking a specially-prepared preparation or simply drinking a large amount of water to dilute their urine. None of these methods are foolproof, and in the case of drinking a large amount of water, having pale urine may be considered a red flag that the person has something to hide.

If marijuana use is putting a person at risk of losing their job, limiting their employment options or interfering with personal relationships, it may be a sign that using the drug is causing more problems than it is worth. In various locations throughout the country, there are marijuana rehabilitation programs and hashish treatment centers that can help an addict get help for his or her addiction and move past it into a sober lifestyle.

Learn more about marijuana rehab centers. Want more information on marijuana abuse? Additionally, here is a list of addiction recovery programs such as Marijuana Anonymous. Or, call 1-866-675-4912 to discuss marijuana rehab treatment options via a free 24 hour helpline.