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Which Flu medications could cause you to fail a drug test?

There are prescribed flu medications that can create a positive drug test result.

Some medications, specifically codeine and hydrocodone, have been reported to affect workplace drug tests. Employees and employers should know these drugs are often prescribed for the flu.


Hydrocode is also used as a cough suppressant and pain reliever in some brands like Lortab. If you are prescribed a medication with Hydrocodone take it as directed. It is an addictive drug which will show up on drug screens that ask for it.


Codeine, used in Tylenol and other medications to counter cough or the aches and pains that come with the flu. It is an opiate. When codeine enters the body and is metabolized, it changes to morphine. Therefore, you may end up with a positive drug screen for codeine and/or morphine. You cannot buy Codeine over the counter in Texas.

Note that Lab based tests generally come with a medical review to eliminate a false positive result by verifying your prescription. So keep that information handy if requested after a drug test. Rapid tests may show this as a presumptive positive result and should be sent for a lab based test to eliminate any possibility that the presumptive positive result was from the prescribed medication.

What about over the counter drugs?

Common decongestants in over the counter cold and flu medications, like ephedrine will not produce a confirmed, positive drug screen in a Lab based test. If you have questions Fastest Labs can help with a drug test prior to your company test. Give us a call at (281) 377-8456