Employee Drug Testing for Medical Marijuana

By: Medical Marijuana Card Doctor

May 14th, 2015

Drug testing reduces the risk of accidents in the workplace, reduces legal liability for companies, and lowers insurance rates.  Occupations that are related to transportation and other safety related professions are required by federal law to undergo drug testing. In most occupations, however, employee drug testing is not required by law but many of the larger companies still utilize it to reap to financial and legal benefits.

Most drug testing procedures test for the presence of (or a predetermined concentration of) medical marijuana in your system that may have been taken anytime in the last 1 to 30 days (1 day for saliva, 4 days for urine, and about 30 days for blood). Arguably, this may be a good thing for the most addictive and destructive drugs, but many states now have laws legalizing the use of marijuana for medical. Should employees have to refrain from using their medication outside of work hours? What if there are no performance issues with this employee? In California, the courts have so far said that employers do have the right to drug test without the presence of performance issues and terminate employees that test positive for banned substances even if they have a recommendation for medical marijuana.

The most common drug testing technique utilized in company medical marijuana testing is urine analysis.  11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (9cTHC) is the marijuana metabolite that most tests detect in your urine.  The length of time 9c THC shows up in the urine after cannabis administration depends on the dose, method of administration and the frequency of use. THC and its metabolites have a high fat solubility meaning it gets easily stored in your body fat. On average if a person who has never had marijuana before smokes one joint of marijuana (approximately 1 gram), 9CTHC will test positive in urine tests about 4 days after use and for those with higher body fat percentage up to one week.  For the frequent smoker of marijuana positive results can show in the urine 46 days after stopping.[1]

There are chances for employees that are not treated with medical marijuana to test positive for marijuana. These test results are called false positives and can be especially troubling for employees.  An employee can have false positive results from taking by mouth nonsteroidal anti-inflammatory medications such as ibuprofen, naproxen, fenoprofen, so it is important to avoid these medications prior to urine testing. Proton pump inhibitors such as pantoprazole and nonnucleoside reverse transcriptase inhibitors can also cause a false positive and must be avoided as well.

An employee can also have negative results after using medical marijuana; these test results are called false negative results.  Testing negative for an employee drug test when using medical marijuana can be advantageous to many employees and has created a market for products to assist with false negative test results. This is evident in the many types of synthetic urines and ingestible products available that are designed to produce a clean urine sample.  It is often difficult to detect if an employee has taken ingestible products as the employee will consume the product prior to taking a drug test.  Synthetic urine is often difficult to detect because employees know to warm the urine to body temperature at the time of the test. Obviously, synthetics are more difficult to use if a witness is required, which is why products like the “Wizzinator” were invented.

Additionally, false negative results can happen after adding Visine eye drops to urine samples.

Another common form of testing is through a saliva sample.  Saliva tests are designed to test for the presence of banned substances taken within the last 24 hours.  Holding the sample collector in the mouth without getting any saliva on the collector can produce false negative results so it is important to ensure saturation of the collector.

Hair samples are also a method of testing for medical marijuana. An employee has to be a frequent user of medicinal marijuana with multiple high doses in order to be positive on this test. This method of testing can have false negatives as well if a patient shaves their hair off.

[1] Ellis GM Jr, Mann MA, Judson BA, Schramm NT, Tashchian A. Excretion patterns of cannabinoid metabolites after last use in a group of chronic users. Clin Pharmacol Ther. 1985;38(5):572-578

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