Marijuana and Drug Testing

The laws surrounding the use of marijuana vary greatly from state to state. Many states have come to accept the use of marijuana for medical reasons, and a few others have even legalized it for recreational use.

But because marijuana is still illegal under federal law, this widely differing legislation can cause problems for a job applicant or employee who tests positive on a drug test.

Federal and State Drug Testing Laws

Under federal law marijuana (cannabis) is classified as a Schedule I substance. Employers in industries that are heavily regulated by the federal government (FAA, FMCSA, FTA, FRA, PHMSA, etc.) are mandated to drug test all new hires and screen employees on a random basis. Non-federally regulated employers aren’t subject to federal laws, but may still have to comply with state and local government laws regulating drug testing.

So how long can marijuana remain in a person’s system?

Though the effects of THC—the main chemical in marijuana—wear off within a few hours of ingesting marijuana, traces of the chemical can remain in the body for weeks. There is no perfect formula for determining exactly how long marijuana stays in someone’s system prior to performing a urine, saliva or hair drug test. However, people who smoked or ingested marijuana in the last:

  • 24-72 hours can fail a saliva test
  • 30-45 days can fail a urine test
  • Up to 90 days can fail a hair follicle test

Factors that can affect how long marijuana stays in a person’s system:

Frequency of use: Someone who has been using marijuana for many years or who uses it daily is likely to have a build-up of THC in their system, meaning it will take longer to leave the body.

Concentration levels of THC: Marijuana can have varying levels TCH potency. If marijuana with a higher THC potency is used, metabolites will remain in the body for longer periods of time.

Methods of use: How marijuana is used can have a significant impact on the amount of time it is detectable. If marijuana is smoked, the THC levels in the drug user’s body will drop within a few hours or days of ceasing use. However, marijuana will still show up on a urine or blood drug test for up to 45 days or more after the last time it was smoked. But if it is ingested, it is metabolized more slowly and will remain detectable longer.

Rate of metabolism: Every person who smokes marijuana has a rate of metabolism that is completely different and this can dramatically alter the way the body breaks down THC. In turn, this can very easily change how many days marijuana will stay in the users system, and ultimately result in a failed drug test.

General Health and Body Weight: THC is stored in the body’s fatty tissue. Those with less fat in their body will clear their system of THC faster than those who have more fat.

Employers have the right to maintain drug and alcohol free work environments through the use of substance abuse screening programs. They just have to make sure they are doing so in compliance with all applicable local, state, and federal laws and regulations. The best practice is to have a comprehensive drug testing policy which clearly informs applicants and employees of all expectations.

For further reference, here’s a great infographic from Quest Diagnostics that quickly illustrates marijuana legislation by state.

We are here to help!

If you have questions about developing a drug-free policy, or about your current screening program, please don’t hesitate to reach out to us. Contact A-Check Global here to get started.

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