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What is being tested?

Cannabis/Hemp, is a plant of the species Cannabis sativa that has psychoactive effects. Marijuana/Hemp contains many chemical compounds that interact with the body, called cannabinoids. The main mind-altering cannabinoid in marijuana is THC (delta-9-tetrahydrocannabinol). The body breaks down THC into several inactive metabolites (e.g., THC-COOH, 11-nor-carboxy-delta-9-tetrahydrocannabinol). Since the metabolites of THC stay in the body for a longer period of time than THC does, most marijuana testing detects the presence of THC-COOH or other metabolites in urine. Some tests also detect the active compound, THC, for example when marijuana testing is done using blood or saliva.

Marijuana leaves can be smoked, prepared and eaten in food products, or ingested as a tincture. Smoking or ingesting marijuana causes a faster heartbeat and pulse rate, bloodshot eyes, and dry mouth and throat. It may cause short- and long-term effects, including impaired short-term memory, altered sense of time, decreased ability to concentrate, altered reaction time, decreased coordination, increased risk of psychosis, and cyclic episodes of nausea, stomach pain and vomiting. Marijuana use impairs driving ability, and accident risk greatly increases if the driver is also drinking alcohol. Marijuana today has higher THC concentrations than in the past, which can lead to greater levels of impairment.

Marijuana as medicine

Some people use marijuana to treat a variety of conditions. Due to legal restrictions on marijuana, its therapeutic effects and safety have been difficult to research.

Natural cannabis may be obtained in some states with a medical marijuana license, an identification document issued by the state with a healthcare practitioner’s recommendation. It allows a patient to obtain, possess, and/or grow marijuana for medicinal use. The process for obtaining these cards varies by state.

Synthetic forms or purified forms of THC and other cannabinoids are available as prescription medications that can be taken by mouth, inhaled, or sprayed under the tongue.


Dronabinol and nabilone are two drugs approved by the U.S. Food and Drug Administration (FDA) that contain THC. They are sometimes prescribed to treat chemotherapy-associated nausea that does not respond to standard treatments.

Cannabidiol (CBD) is a compound related to THC that is a product of the marijuana plant. It is available in liquid form (CBD oil) as an FDA-approved medication that may be used to treat pain and inflammation and some epileptic seizures. Some “herbal supplements” also contain CBD but are not regulated by the FDA. Unlike THC, CBD is not intoxicating—it does not make people “high.” However, because CBD is derived from the marijuana plant, it may contain variable amounts of THC.

Nabiximols is a marijuana-derived prescription drug that contains THC and CBD. It may be used to treat muscle control problems in people with multiple sclerosis (MS). Though this drug has not been approved by the FDA, it has been approved for use in Canada, the United Kingdom, and some European countries.

Anything that contains THC has the potential to be detected as THC or THC-COOH in a marijuana test. In medical cases, drug testing results are typically reported to the physicians who ordered the tests and they interpret the meaning of results in the context of the medical cases. To aid the interpretation of results, patients should notify their physicians of any over-the-counter or prescription medications (including marijuana) or supplements they are taking.


Marijuana testing

To test for marijuana, healthcare practitioners may send urine samples to a laboratory for screening or they may perform a test in their office. Testing may be performed with point-of-care tests, which are typically small strips that are dipped into the urine and interpreted by the appearance or absence of a colored line on the strip.

Positive screening tests for marijuana are presumptive. This is because all drug screening tests have the potential for false-positive results. Therefore, screening tests that are positive are often confirmed with a second test, which is referred to as a confirmatory test. Confirmatory tests are usually more sensitive and specific than screening tests. Confirmatory testing is usually performed with an instrument called a mass spectrometer. Types of mass spectrometry tests used for confirmatory testing include gas chromatography/mass spectrometry (GC/MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Additional testing may also be performed to identify whether any substance has been added to the urine sample, such as water, bleach, or other types of chemicals (adulterants) in an attempt to interfere with the test result. If adulteration is suspected, the test may be reported as invalid or adulterated.

Urine samples may also be identified as dilute. Dilute urine may be produced if an individual drinks large amounts of water or other liquids prior to testing. Dilute urine may also result from some medical conditions. If an individual adds liquid such as water to a urine sample, this may also cause dilute urine. It may not always be possible to determine how the urine was diluted. If the urine is so dilute that the results are not reliable, the test may be reported as invalid or adulterated.