What Causes False Positive For On A Drug Screen For Marijuana?

Posted on Mon, 7 Jul 2014

Question: I recently tested positive for thc on a drug screen. I have not smoked marijuana since 1986, Two days after the MRO notified me of results, I discovered that my wife had given me two of her phenegran pills when I was nauseaus. I did not know what she gave me was a prescription drug. How can I reslove this?

Answered by Dr. Jonas Sundarakumar (1 hour later)

Brief Answer:
Request for hair follicle test

Detailed Answer:
Hello and welcome to Healthcare Magic. Thanks for your query.

Promethazine (Phenergan) is known to cause false positives on a drug screen for Marijuana. In your situation, I would advise you to inform the MRO about your recent intake of Phenergan pills. You can request him to do a hair follicle testing which would be more specific for detecing Marijuana. A negative hair follicle test would be sufficient to prove that the urine drug screen was only a false positive.

Wish you all the best.

Regards,
Dr. Jonas Sundarakumar MBBS., DPM., MRCPsych.(U.K.)
Consultant Psychiatrist

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Above answer was peer-reviewed by : Dr. Prasad