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Marijuana Drug Testing Facts

Marijuana drug tests are administered by parents, employers, probation officers and other authority figures to detect if a person has used the drug. There are different types of tests, including body fluid and hair follicle. The test can tell if a person has taken the drug but not when or how much of the drug was taken.

  1. Body Fluid Testing

    • Marijuana use can be detected by testing the urine, saliva or blood Analysis specimens are collected from an individual, sealed and sent off to a laboratory that tests the specimen for various drugs, including marijuana. With a saliva test, detection begins 24 hours after the drug is taken. Blood tests are the most expensive but most accurate marijuana drug test.

    Hair Follicle Testing

    • Testing by a hair follicle can trace marijuana usage back as far as 90 days. This is because as a person's hair grows, the marijuana used is encased in the hair shaft.

    False Positive

    • Some marijuana drug tests can pick up other drugs that a person is taking. For example, prescription antibiotics and pain pills can cause a marijuana drugs test to be positive. It is best for a person being tested for marijuana to let the employer or test administrator know of any prescription drugs that he is taking. The drugs need to be legally prescribed and not being abused by the person.

    When Drug Was Taken & How Much

    • When a drug test is administered and a person tests positive for drugs, there is no way to determine when the drug was taken. No matter what type of drug test is taken, including urine, blood or saliva, the only detection the test can make is if a specific drug or drug metabolite is present at the time the test was performed. There are very broad estimates as to how long a drug may have been in a person's system; no fluid test taken, regardless of the method used, can include a time variable. In addition to the time variable, the tests can not tell how much of the drug a person has taken.

    Detection Time Period

    • Tests can detect marijuana in a person's system during certain time periods. The amount of marijuana a person uses is a big factor in how long drug tests can detect if a person has used marijuana. For instance, if a person has a single usage of marijuana, a urine drug test can detect the drug in a person's system for 48 to 72 hours after usage. For a person who has a more chronic or habitual use of marijuana, the drug test will detect the drug through a urine sample for up to 12 weeks depending on the duration, quantity and frequency of usage.

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