Can Mucinex DM cause false positive drug tests? 

Can Mucinex DM cause false positive drug tests? 

Mucinex DM is not likely to cause a false positive drug test. However, it does contain Dextromethorphan, which is a cough suppressant (1). Dextromethorphan does have some chemical similarities to Opioids and that could cause a false positive drug test, but that is extremely rare (2). 

Even if you struggle with a Dextromethorphan-induced false positive drug test, there are more selective confirmatory tests to help you determine the exact chemical causing such a result. 

The primary method of drug test is through urine immunoassay and this method is not so promising. The antibodies present in the technique can mistakenly bind with Dextromethorphan, and this could give a false positive for Opioids. (2)

Techniques like Gas Chromatography – Mass spectroscopy (GC-MS) are more sensitive and can be used if the urine analysis fails to work well. (3)

How long does Dextromethorphan stay in your system?

Dextromethorphan, the active ingredient in many cough medicines, can stay in your system for about 2 to 4 days (4). However, this can vary depending on factors such as age, metabolism, and the dose you took. 

After taking a dose, your body breaks down the dextromethorphan, and it is eventually eliminated from your system through urine and faeces. 

It’s important to follow the recommended dosage instructions and not take more than what is advised on the label to avoid any potential risks or side effects associated with higher doses. 

How to prevent Mucinex DM from causing a false positive in a drug test?

To prevent Mucinex DM from causing a false positive in a drug test, it’s essential to inform the testing facility or healthcare provider about any medications you are currently taking. 

As we have discussed, Mucinex DM contains Dextromethorphan, which could potentially show up as a false positive for opioids in some drug tests. Providing this information beforehand allows the test administrators to take it into account and interpret the results accurately.

If you are concerned about potential false positives, you can also ask for a confirmation test to verify the specific substances in your system. Always follow the recommended dosage and use Mucinex DM as directed to minimize any potential risks.

If you have any doubts or questions, don’t hesitate to talk to your healthcare provider before the drug test to ensure accurate results.

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LABEL: MUCINEX DM- guaifenesin and dextromethorphan hydrobromide tablet, extended-release. DailyMed [Internet]. Available from:


Alyson Schwebach, Jennifer Ball. Urine Drug Screening: Minimizing False Positives and False Negatives to Optimize Patient Care. US Pharm. 2013;38(12):1-6. Available at:


Ramoo B, Funke M, Frazee C, Garg U. Comprehensive Urine Drug Screen by Gas Chromatography/Mass Spectrometry (GC/MS). Methods Mol Biol. 2016;1383:125-31. doi: 10.1007/978-1-4939-3252-8_15. PMID: 26660182.


PubChem [Internet]. Bethesda (MD): National Library of Medicine (US), National Center for Biotechnology Information; 2004-. PubChem Compound Summary for CID 5360696, Dextromethorphan; [cited 2023 July 19]. Available from: