What Causes A False Positive Result For Methamphetamine In Urinalysis Test?

Posted on Tue, 9 Feb 2016

Medically reviewed by Ask A Doctor - 24x7 Medical Review Team

Tue, 9 Feb 2016 Answered on

Thu, 9 Jun 2016 Last reviewed on

Question : Yes, I have in the past and recently tested positive for methamphetamines in a drug screen urinalysis, but the line was very faint and didn't look any differently than the one next to it just a little maybe, it took three deputies looking at it closely with a fine tooth comb until they said after :30 minutes it was positive. I disagreed and told them I was on medications that had caused this same problem before, and before I took the test I told them I was on Zanax and Claritin D 24 Hr 240/mg tablets daily for my allergies and had been for 20 years and I had ran into this problem before only to have a more accurate lab analysis done to confirm my innocence, Please give me your input!!!!

Answered by Dr. Dr. Matt Wachsman (2 hours later)

Brief Answer:
This happens a lot

Detailed Answer:
decongestants are very similar structures and are well known to cross react on the dipstick and are differentiable with the mass spect test.

furthermore it is common to get false positives without a clear reason on the dipstick

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Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar