Last updated on October 2nd, 2020 at 10:00 am
“But I Only Used One Time, Thirty Days Ago” Part I
When employers feel pressured to loosen-up their drug and alcohol policies to provide more room for the use of marijuana, one popular argument is that presence-in-system testing simply is not fair. We’ve all heard the outcry, “An employee can be fired for smoking weed one time, thirty days ago, and that’s just not right … they aren’t even impaired!”
This leads to demands for an impairment test – or – for an employer to “prove” impairment before taking action based on a drug test result.
These arguments and questions seem reasonable until the truth gets involved.
We essentially have two separate issues to unravel in this conversation. We’ll start with the first, which is the “thirty days ago” scenario for a marijuana drug test. The second, proving impairment, will be featured in a future blog post.
One of the most widely misunderstood and often repeated myths is that one-time marijuana use can show up on a drug test thirty days later. This is tantamount to the ultimate trick-question. Far more people fail to see the problems with the statement than those who might fail the drug test.
The key tricky phrase is “one-time use”. The one-time user of cannabis is NEVER going to fail a drug test thirty days later. Not in urinalysis, not in hair, not in oral fluid, nor any other means of drug testing. When using the standard cut-off levels, nearly all urine drug tests will be negative 3-5 days following use.
The confusion comes from chronic marijuana use. Those who partake of marijuana products with regularity (daily to weekly) are considered chronic or heavy users. The chronic user experiences saturation of Carboxy-THC which saturate the fat cells, to include the brain.
When the heavy user ceases cannabis usage it could take weeks for the THC to leave the system and for that individual to produce a clean drug test result.
In no uncertain terms, when one hears the excuse, “I used once thirty days ago” … this is a falsehood. They may have ceased use thirty days ago, but they would have been a heavy marijuana user in order to obtain a positive drug test.
What this means for an employer: this is not a valid excuse for a failed drug test, there is more here than meets the eye. We will explore this further in Part 2 of this conversation. In the meantime, make sure your drug and alcohol policy is up-to-date and maintain your drug testing practices with confidence.
 Workplace Drug Testing in the Era of Legal Marijuana, Institute for Behavior and Health (2014) Washington D.C.
By Jo McGuire
Jo McGuire is a Denver native who served on the Colorado Governor’s Task Force to implement the regulatory framework for Amendment 64, representing employer’s rights to safe and drug free workplaces. As a national expert, she has authored dozens of articles for a variety of trade magazines and is a sought-after conference speaker and webinar presenter on the impact of marijuana in the workplace. She also assists TSS Inc with special projects. Jo is the Chairman-Elect of the Drug and Alcohol Testing Industry Association (DATIA) and chairs the Marijuana Outreach Committee.
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